How do I check how many updates there are to the CD's that I own?

Photoshop Elements 4 does not require activation to work, just the serial number.

It may not work on the current operating system, however.

And just to clarify:

An update is a modification to an existing program.

An upgrade is a new program.

I don't know, but I will GUESS that those old programs will not activate

The CS2-CS3-CS4 activation servers have been removed from service
-https://helpx.adobe.com/creative-suite.html?promoid=19SCDRQK
-So even if you have a disc or saved download, CS2-CS3-CS4 are completely dead

You cannot get and upgrade: too old.

Have to buy new and if you do check your machine if it can handle the software.

Edit:

Besides, everything is now subscription or a license, depending on the software.

Moved question from Premiere Pro to Elements forum.