Random vertical lines on the screen

That’s usually a symptom of a graphics hardware failure.

Try Safe Mode, and try Diagnostics or Hardware Test. Safe Mode rebuilds performance caches, and runs in a simpler graphics mode, and disables kernel add-ons. The diagnostics/test don’t find all errors.

If you don’t have an Apple ID, you’re going to have trouble with upgrades for macOS and apps, as that’s all tied to your Apple ID. Associating with an Apple ID usually means getting a backup, wiping, and reinstalling, and purchasing any commercial add-on apps.

You’ll want a backup or two here in any case, as this Mac is headed for repair or replacement.

MrHoffman has you covered pretty well. :)

Have you blown the dust out of the intakes lately?

What temperatures does this App report?

This App can be used to speed up the fans, all my iMacs would be dead without it.

MacFansControl…

https://www.crystalidea.com/macs-fan-control

An Apple Store or an Apple authorized service provider will usually run Apple’s own (and better) diagnostics at no charge, and take a look at the display symptoms.

Contact Apple Support, and ask about bringing it in for a look.

If this is an older system, you’re probably headed for a newer-used or for a new Mac. (If this Mac has a hard disk, the SSDs used in newer systems are massively faster, too.)

But then this could be some easily-replaced part, too.

Without access to the system, it’s difficult to determine what’s wrong.

Adjusting the fan speeds (up) might keep a marginal bit of display hardware from corrupting the display, or not. Whether that’s due to the hardware itself failing, or dust that’s blocking the cooling, or some other issue? But I’m skeptical around fan-speed tools in general, and would seriously discourage ever dropping fan speeds below the speed that the Mac itself is calling for.

It does sound like a HW issue, were you able to install MFC & see the temps?

would seriously discourage ever dropping fan speeds below the speed that the Mac itself is calling for.

Will add that or something to that effect, thanks...