Implementing gMSA account for SQL FCI
Does implementing gMSA works for 2 node SQL FCI and 3 or 4 Node Always on AG,s?


Yes it does work. 


  Since I just want to run SQl server with that gMSA account is there any special permissions needs to be granted at server or database level while running both SQL and agent services?


Nope, the installer will take care of that.


  Please advise any catch of implementing gMSa here.


If certain windows services don't start before SQL Server, then authentication can't take place and SQL Server will fail to start up. This doesn't happen very often and generally when it does there is some other issue with the server that is causing this symptom and behavior.