Advice please re how best to delete old Applications

I am about to try a backup of my iMac (PowerPC G4) using SuperDuper which I saw recommended for this purpose. Before I did this I thought it a good idea to wipe all the old Apps and files that I no longer need off the Imac.

When I had a look at the applications listed under System Profile I see that I appear to have lots of old versions of Apps as well as the newest one - mistakenly in my ignorance I had thought as new software was loaded old versions were wiped off automatically eg I seem to have about 6 versions of Adobe Reader shown from Version 5 forward.

My question is can I safely remove anything which appears to be an earlier version of software in the Applications list and what is the best way of doing this so that no traces of these Apps are left to use up space I desperately need?

DaveG