Topic: Why do some Nintendo UK games have UKV-1 or 2 codes?

I was just wondering what the difference is between UKV, UKV-1 and UKV-2?

Ok, UKV1-2 appear to be later prints of UK games. But would the manuals and cartridges from different prints ever be officially combined or would they never be combined unless owners took a cartridge and manual from different prints?.

For instance the cartridge would say UKV and the manual would say UKV2.

I'm not sure on the difference but I'm sure that some UKV titles don't work on my RetroDuo Portable, take a look at Super Mario All-Stars... https://photos.app.goo.gl/pfKmngGQKYFheGU77

I've seen videos of people playing that game on it but it doesn't work on mine.

Could be down to when Nintendo has to make even the slightest change. Whether it be something as small as legal text nobody is going to care about.
I think NES region PAL-A (including UK) was the region with NES games that could be used the "Mattel or NES version of the Nintendo Entertainment System."
Not sure what they did over in like France (PAL-B) where their NES games could not be used with the NES version of the Nintendo Entertainment System. How did they play them?