I just bought a 2020 iMac 27 and want to connect a 2011 iMac 27 as a 2nd monitor can that be possible?

Also, the support article you arrived here from should have already provided you with the answer to that question.

• The other Mac that you're connecting it to must have been introduced in 2019 or earlier and have macOS Catalina or earlier installed. -- In this case that would be your 2020 iMac, which would not qualify.

No, unfortunately.