How to make a common registration on 1 key of two Bitrix projects?

Question

1C-Bitrix

Good afternoon. Such situation
There is a site where bricks and toys are on sale for example. Everything hangs on 1 person. Bitrix key is big business.
The task is to separate the toys from the bricks, take out everything within the framework of one license (!) And make a common registration system (use 1bd for two). Just hide the information block with bricks on one site, and open it on another.
Questions:

• Is it allowed to do this within 1 key?
  
• How to make a general registration system?
  
• How to set up 2 domains with 1 database? The location will be on the same hosting. The second site will be placed on a subdomain.
  

Answer 1

If you use bitrix-env, then you need to create a new host with the "link" parameters, or if without bitrix-env, create a new hosting and link it with symbolic links to the main site. And properly configure the sites in the admin panel. Then, when developing, take into account when setting up the information blocks themselves and developing components. Don't forget about templates and mail events.
You can read here

Answer 2

I highly recommend this article on setting up multisite.
the second site is made literally in 15 minutes, but you can spend a lot of time on transferring data and dividing the project)
domains are configured in the hosting control panel - one domain for one directory, the other for another. if your panel does not have this - ask the technical support of the hosting.