How to check ssh2 setup and disable password login?

Question

linux

Carried out a number of actions to improve security on the server:
-installed the ssh2 module -changed
the port for ssh from 22 to 20111
-closed extra ports, left only 80, 443, and 20111
-disabled root
login -disabled login by passwords, made login by keys .
What are some ways to make sure it works?
So far I know only two ways - scan ports with nmap and try to access the server using putty

Answer 1

close the port for sssh with a firewall (leave it only for your reals)
mastering port knocking
with regard to overweighting the port makes sense only if it costs something for the autobahn when scanning.
and it is not clear why he did not use the key + password combination

Answer 2

log in with any ssx client on port 22 and change it with the login