IS IMAC 27" LATE 2010 CATALINA COMPATIBLE?

The end of the road for a 2010 is 10.13.6 High Sierra. The reason you cannot go beyond HS is later versions of Mac OS require GPUs that have Metal (please Google Metal for additional info) built in. Your GPU cannot be updated so that means you are left with HS as the last version of Mac OS you can use on a 2010.

In short, if you want or need Catalina or later, you need to get a newer Mac.

No. Catalina requires a Late 2012 or later iMac.

Your welcome.