Hello, I recently bought Jazz Jackrabbit 1.

AFAIK it's the US version. I'm still waiting for the game. Meanwhile I've looked whats inside the box. I should get this disk.
Then I've noticed there's a EU version of JJR1. I'm confused because it should have four disks: EU disk

So my questions are:
1. Does the US versions contain only one disk and the EU four? If yes what are the differences of the games?

2. At least does the US version contain all six episodes?

3. What is the origin release/version? The US one? Or were both versions released same time?
To be honest the EU thing looks a bit like a budget version...

I believe there are plenty of JJ1 distributions besides the ones Epic distributed through their mail order and partners for the shareware floppy, registered floppies, and CD version. For example, my CD version was distributed by 'Best Buys' in select EU countries, and the 4 floppy version you linked to is a German one.

However, no registered version should be on 1 floppy (as far as I'm aware) if you bought the full version consisting of all 6 episodes.

So, if it got delivered, I'm curious how many floppies and episodes you got?

I received it some days ago and I opened this sealed box.

It contais only one disk. I assume it's shareware in a nice big box.
I'll tell more once I got my ordered floppy drive.

Yep, that's actually a fairly well-known shareware-only release of the game. The box is nice, but that's about it.

there is another jj1 boxed release with only the first three episodes, it's called jazz jackrabbit trilogy.

Yeah. Better than the shareware-only box, but still not great.
I suppose if you can get ahold of episodes 4-6 on floppy, trilogy would be a fairly affordable option for getting the rest, but then you'd still be missing episodes A, B, and C. And of course, there's the Holiday Hares aswell.