If you are taking Magento2 [Files + Database] from server & setup on localhost & while trying to open Admin , It will be not opened, due to cookie domain values specified for a particular domain name.

Solution: There are following below command need to ben run

[1]-: Run select query , to check how many cookie domain values are present in Database

select * from core_config_data 
WHERE path = "web/cookie/cookie_domain"

[2]-: Run update query:

To update all path = “web/cookie/cookie_domain” into 0

update core_config_data
set value="0" 
WHERE path = "web/cookie/cookie_domain"

Once run query all path = “web/cookie/cookie_domain” values will be converted into 0, check again by using select query

select * from core_config_data 
WHERE path = "web/cookie/cookie_domain"

Note: Here only one cookie domain value, if some cases multi store, there
are multiple path = "web/cookie/cookie_domain" & each path value having domain name exists, so you need to converts all 
path = "web/cookie/cookie_domain" values into 0

Finally, localhost Magento 2 admin issue has been resolved.

If you getting error like

installation failed reverting ./composer.json to its original content

Solution: There is following below command need to be run

Composer update

Running format this command

Once command done, Finally, issue will be resolved.

There are following below steps to do URL rewrites for Product, Category, CMS Pages

[1]-: The following below command to delete Product, Category & CMS Page URLs from

Table url_rewrite & catalog_url_rewrite_product_category

delete from url_rewrite;
delete from catalog_url_rewrite_product_category;

[2]-: The following below command to install by using Extension

OlegKoval_RegenerateUrlRewrites

that is responsible to regenerate Product, Category & CMS Page URLs

Install
composer require olegkoval/magento2-regenerate-url-rewrites

Once command done, It is stored location in side Vendor folder as below

[3]-: The following below command to enable olegkoval Extension , that is responsible to regenerate Product, Category & CMS Page URLs

Enable
php bin/magento module:enable OlegKoval_RegenerateUrlRewrites

[4]-: The following below command to regenerate Product, Category & CMS Page URLs

Regenerate URL
php bin/magento ok:urlrewrites:regenerate

Note: If you use some external cache mechanisms (e.g.: Redis, Varnish, etc.) - please, refresh this external cache.

Finally, Website / Store, Product, Category & CMS Page URLs has been regenerated.

Step-1: By Using Magento 2 Admin

• Go To Magento 2 Admin
• Catalog–Products: select Simple Products, which you want to converts into Virtual products.

• Click on Edit

• Go To Weight: “The item has weight” for Simple Product already mentioned.
• To Converts into Virtual Product, “select Item has no weight”

• Step-2: By Using Database SQL Query

update catalog_product_entity 
set type_id = 'virtual' 
where type_id = 'simple'

Note: Be careful, this query will be converted all Simple Products To Virtual Products

Note: If user wants to convert specific Simple Products To Virtual Products, below query need to run

update catalog_product_entity 
set type_id = 'virtual' 
where type_id = 'simple' and sku in ('BSX55MOLCG','BSX55MOLCLW','BSX55MOLCMW','BSX55MOLWWH')

Step-1: By Using Magento 2 Admin,

• Go To Magento 2 Admin
• Catalog–Products: select Virtual Products, which you want to converts into simple products.

• Click on Edit

• Go To Weight: “The item has no weight” for Virtual Product already mentioned.
• To Converts into Simple Product, select Item has weight & put
  weight value.

• Finally Click on Save button & Virtual Product will be converted into Simple
  Product.

Step-2: By Using Database SQL Query

update catalog_product_entity 
set type_id = 'simple' 
where type_id = 'virtual'

Note: Be careful, this query will be converted all Simple Products To Virtual Products

Note: If user wants to convert specific Simple Products To Virtual Products, below query need to run

update catalog_product_entity 
set type_id = 'simple' 
where type_id = 'virtual' and sku in ('BSX55MOLCG','BSX55MOLCLW','BSX55MOLCMW','BSX55MOLWWH')

• https://www.paulsmith.com
• https://www.omegawatches.com
• https://www.paperchase.com
• https://www.paulsmith.com
• https://www.paperchase.com
• https://www.cyclerepublic.com
• https://www.bulkpowders.co.uk
• https://solgirl.com
• https://www.coxandcox.co.uk
• https://www.sigmabeauty.com
• https://www.bulkpowders.co.uk
• https://www.boodles.com
• https://royalmen.com
• https://rattanfurnitureuk.co.uk
• https://girav.com
• https://addapearl.com
• https://onlinespyshop.co.uk

There are following below Magento 2 tables need to be deleted, before going to Production or Live

--SET FOREIGN_KEY_CHECKS = 0 Compulsory otherwise Foreign Key Based Table will be not deleted --

  SET FOREIGN_KEY_CHECKS = 0;

-- Starts Truncate Quote & Sales Order & Other Tables --

TRUNCATE TABLE `gift_message`;
TRUNCATE TABLE `quote`;
TRUNCATE TABLE `quote_address`;
TRUNCATE TABLE `quote_address_item`;
TRUNCATE TABLE `quote_id_mask`;
TRUNCATE TABLE `quote_item`;
TRUNCATE TABLE `quote_item_option`;
TRUNCATE TABLE `quote_payment`;
TRUNCATE TABLE `quote_shipping_rate`;
TRUNCATE TABLE `reporting_orders`;
TRUNCATE TABLE `sales_bestsellers_aggregated_daily`;
TRUNCATE TABLE `sales_bestsellers_aggregated_monthly`;
TRUNCATE TABLE `sales_bestsellers_aggregated_yearly`;
TRUNCATE TABLE `sales_creditmemo`;
TRUNCATE TABLE `sales_creditmemo_comment`;
TRUNCATE TABLE `sales_creditmemo_grid`;
TRUNCATE TABLE `sales_creditmemo_item`;
TRUNCATE TABLE `sales_invoice`;
TRUNCATE TABLE `sales_invoiced_aggregated`;
TRUNCATE TABLE `sales_invoiced_aggregated_order`;
TRUNCATE TABLE `sales_invoice_comment`;
TRUNCATE TABLE `sales_invoice_grid`;
TRUNCATE TABLE `sales_invoice_item`;
TRUNCATE TABLE `sales_order`;
TRUNCATE TABLE `sales_order_address`;
TRUNCATE TABLE `sales_order_aggregated_created`;
TRUNCATE TABLE `sales_order_aggregated_updated`;
TRUNCATE TABLE `sales_order_grid`;
TRUNCATE TABLE `sales_order_item`;
TRUNCATE TABLE `sales_order_payment`;
TRUNCATE TABLE `sales_order_status_history`;
TRUNCATE TABLE `sales_order_tax`;
TRUNCATE TABLE `sales_order_tax_item`;
TRUNCATE TABLE `sales_payment_transaction`;
TRUNCATE TABLE `sales_refunded_aggregated`;
TRUNCATE TABLE `sales_refunded_aggregated_order`;
TRUNCATE TABLE `sales_shipment`;
TRUNCATE TABLE `sales_shipment_comment`;
TRUNCATE TABLE `sales_shipment_grid`;
TRUNCATE TABLE `sales_shipment_item`;
TRUNCATE TABLE `sales_shipment_track`;
TRUNCATE TABLE `sales_shipping_aggregated`;
TRUNCATE TABLE `sales_shipping_aggregated_order`;
TRUNCATE TABLE `tax_order_aggregated_created`;
TRUNCATE TABLE `tax_order_aggregated_updated`;

-- Finish Truncate Quote & Sales Order Tables --

-- Truncate Customer tables

-- Starts Truncate Customer Data & Customer Address Tables --

TRUNCATE TABLE `customer_address_entity`;
TRUNCATE TABLE `customer_address_entity_datetime`;
TRUNCATE TABLE `customer_address_entity_decimal`;
TRUNCATE TABLE `customer_address_entity_int`;
TRUNCATE TABLE `customer_address_entity_text`;
TRUNCATE TABLE `customer_address_entity_varchar`;
TRUNCATE TABLE `customer_entity`;
TRUNCATE TABLE `customer_entity_datetime`;
TRUNCATE TABLE `customer_entity_decimal`;
TRUNCATE TABLE `customer_entity_int`;
TRUNCATE TABLE `customer_entity_text`;
TRUNCATE TABLE `customer_entity_varchar`;
TRUNCATE TABLE `customer_grid_flat`;
TRUNCATE TABLE `customer_log`;
TRUNCATE TABLE `customer_log`;
TRUNCATE TABLE `customer_visitor`;
TRUNCATE TABLE `persistent_session`;
TRUNCATE TABLE `wishlist`;
TRUNCATE TABLE `wishlist_item`;
TRUNCATE TABLE `wishlist_item_option`;

-- Finish Truncate Customer Data & Customer Address Tables --


-- Starts Truncate Review tables --

TRUNCATE TABLE `review`;
TRUNCATE TABLE `review_detail`;
TRUNCATE TABLE `review_entity_summary`;
TRUNCATE TABLE `review_store`;

-- Finish Truncate Review tables --

Magento 2 All Database Tables [500 & more Tables]

Which Magento 2 database table store customer’s Email Data

Which Magento 2 Database Table Store Customer Newsletter Data

Which Magento 2 database table store customer’s shipping and billing address

How To Remove Sales Order Data & Customer Data in Magento 2

Which Magento 2 Database Tables Store Customer Rating

Which Magento 2 Database Tables Store Customer Review

Which Magento 2 Database Tables Store Customer Wishlist Products

Which Magento 2 Database Table Store Patches

Which Magento 2 Database Table Store Static Blocks & Its Details

Which Magento 2 Database Table Store CMS Pages & Its Details

Which Magento 2 Database Tables Having All URLs Storage

Which Magento 2 Database Tables Store Sales Order Data

Which Magento 2 Database Tables Store Sales Invoice Order Data

Which Magento 2 Database Tables Store Sales Tax and Its related Data

Which Magento 2 Database Tables Store Catalog Price Rules

Which Magento 2 Database Tables Store Cart Price Rules

Which Magento 2 Database Table Store Patches

Single Sign-on (SSO):: It is an authentication process that allow users to access multiple applications with same login credentials of Magento 2. Using this user can enter the login credentials in the third-party application and be logged in to Magento 2 store simultaneously.

“Single sign-on is an authentication method that allows a user to log in with a single ID and password to multiples applications simultaneously”

“Single Credential that enables users to log in to multiple applications and websites”

This allows faster access to applications. The customers can use their existing credentials for logging into various third-party applications such as UVdesk, The user can use one set of credentials for various platforms and won’t have to remember multiple passwords for each login.

Magento 2 using multiple stores, blog etc., by using single User ID / Password, user can enable to login multiple Magento 2 stores & blog