How not to lose positions and redirect traffic from subdomain to domain?

Question

Search Engine Optimization

The essence of promotion in my case is that I promote the main domain, while keeping the main domain closed for users, leaving it open only for bots. (The domain and subdomain are identical in content)
And when you go from the search on the main domain, I throw a redirect to the subdomain.
From the side of the main domain, I only allow bots - I send the rest to the subdomain
. I have a closed robots on the subdomain so that the bots do not enter and do nothing.
By doing this, I am trying to achieve the result when the main domain is in the search, but if I go from the search, I always get to the subdomain.
But here's the problem and the problem is this. I made a mistake and incorrectly closed the robots on the subdomain, in connection with this, both the main domain and the subdomain got into the index, and the main domain and subdomain have positions in the search, and the subdomain has positions higher than the main domain, and everything should be on turnover.
That is, positions should have only the main domain without a subdomain.
Actually, the question is, how to be now in this situation? Close robots on a subdomain? After that, I will lose the current positions of the subdomain. Put a canonical on all pages of the site with a redirect to the main domain? What will happen to the positions then, will it give all the weight from the subdomain to the domain?
Or, as an option, is it to put a redirect on the current subdomain (send all bots to the main domain) and display the canonical for users?
A very delicate and difficult question for me, I am very afraid to break everything that is now in terms of positions.

Answer 1

We are launching a standard move for robots by 301 from the subdomain to the main one.
There - we give the opportunity to robots to go to links 200 and display content from the main domain.
For users, we leave everything as it is: when switching from a search, we throw it on a subdomain.
Upon completion of the linking, we close access by ip for all robots (404) to the subdomain and at the same time! access to index-date (robots.txt, and other files).