In the EU enforcement of traffic rules is a matter of member states, but many rules are codified on EU level, at least for what is street legal. That abomination above violates the common rules already quite clearly. It is thinkable that one can grey import individual cars and get a custom license for that but even than some modifications will be required, but that depends on the local authorities. In any case it must be hard or expensive as you basically don't see that kind of nonsense on the streets.

If you are seen driving an obviously non-street legal car and can't come up with papers to the contrary your vehicle gets immediately grounded, towed and you can call a taxi. If you are a repeat offender chances are you could lose your drivers license and when you are driving without one consequences can get much worse.

But hey, you can still get an Aixam for your mobility needs without a drivers license: https://www.aixam.com/en/ They even sell "Crossovers" for those with increased compensation needs.

They can't. This class of vehicle isn't legal in the European Union it's why the cybertruck isn't legal (there's a whole bunch of other problems with it as well but the weight limit is a major problem). If you wanted anyway just to have it on private property you're out to luck. Someone did train import to cybertruck into the UK and had it confiscated.

I think there is a classification for vehicle that you can get if it's something like a race car or rally car but it can't be driven on the road and has to be driven around on a truck to move it.