How do I upgrade my Craig tablet to 4.4? - Tablets & eReaders

You presumably mean versions of Android operating system.

I went in to this a while ago owning a couple of little used but old tablets and now many of the apps no longer work and can't be updated.

I read an article by a boffin who had tried to update Android. He got inside the structure of Android and after much fiddling around he made it better so it would accept a few updated apps but most of the important ones still wouldn't go.

The reason for this is Android is as unlike the Windows OS as it is possible to get. Tablet and phone manufacturers buy a current version of Android and then they have to modify it to make it work with their electronics and that makes their version almost unique. Updates have to come from that source. Some manufacturers provide updates but many don't and when it has outlasted it's usefulness it is time to replace it with a newer unit. If update is in the menu it will have a longer useful life but lots of label engineered units and budget models don't have that option meaning the "manufacturer" has no intention of providing updates.

The boffin concluded for all practical purposes there is no way to load a later version of Android onto older electronics.