Is the 9.2.10 Relay and Clients supported by the Server which are at 9.2.5.1?
I know that the server must have the highest version in your environment.
so the server at 9.2.10 can support the relays and clients at lower version but not vice versa.
You should have relays at the same level as your server. It is not a good idea to have the infrastructure components on different versions. The Agents often are but relays should be current
Clients in general work if they are higher versions than the server (we actively try to make them work - but that may not be the official support policy so caveat emptor)
I have some relays which have higher (9.2.8.74) version than the server (9.2.5.1). Is it safe to uninstall the higher version e install an older version in these relays?
I think you are OK there. I wouldn’t go out of the 9.2 range for your situation. In general having the relay in the same major.minor should be OK. Going out of that (say installing a 9.1 or 9.5 relay in your case) I would not recommend.
When I say not at the same level, it is the major.minor I am meaning. The specific patch shouldn’t matter unless it has fixes you need. A server is partially just a large relay remember that so if you upgrade your relays the server probably needs upgrading as well.