elements on iMac

If you want to stick with elements and it limited support you'll have to get a new version. 
if you want more than a couple of months of support and (almost no) updates you could thing of other software. Personally I switched to affinity photo. Works fine, is cheaper and gets wayyyyyy longer support. 
It does not have the organiser function, but the editor is just as good. And the lack of support was for me a big issue. 

. . .  and you will also have to use Rosetta 2 to operate the program.

Elements 13 will not work on a Monterey machine, particularly with an M1 chip.  So, yes, you will need to upgrade to Elements 2022.

That's a pretty sweeping question. I'll try to get the ball rolling, although I don't have anywhere near as much knowledge as some who read these discussions. Please choose "About this Mac" from the Apple menu and share with us some of the information you see, including OS version and machine model.