Hi,
I have a problem with SNMP server.
This is my SNMP settings: I've tried different settings, but nothing works.
Tried changing versions, interfaces, etc.
There is nothing in firewall regarding UDP and/or 161 port.
Is there some snmpwalk command equivalent that I could execute in routers terminal?

Just tested, those settings will work, as long as you have an input rule for LAN traffic to your router.
Can you paste your firewall config?

It was indeed input rule missing. There was other input rules, but not for new connections.
With new rule it works. So thanks for pointing out possible cause.