those are multiple problems.
the first one with the TLS Version, I’m not too sure about how to fix it.
The second one command does not exist is a known one to me.
check with icinga2 object list --name <command> if the agent knows the check.
Also check the post michi wrote. Check your config deployment via the director, I would guess there are some problems drin as they are not leaving the staging area. Also check my old post about the same issue Icinga Update 2.11; Director Commands not available