What version of Photoshop are you having problems with and what system is it running on? If you are on subscription you should just reinstall.
If you have CS2 you may not be able to reinstall due to shut down of Adobe authentication servers.
Regarding old versions, I am currently running Photoshop CS2 on XP and Version 5 on Windows 10. No problems with these old versions. But that's my personal experience. Yours may be different.
Actually, CS2 was until very recently still available on Adobe's site, along with the authentication key. Yes, they shut down the authentication servers for this nearly 7 years ago.....but kept it available because there were still so many professionals using these older versions, for whom they were perfectly adequate for the tasks at hand.
I myself actually bought this thing more than 16 years ago. I still use it to this day, now running under WINE in Linux, alongside the G.I.M.P; I'm so used to both of them, I can switch back & forth mid-project, and just pick straight up from where I left off.
Mike.