Welcome. All of europe has that 25kw rule and it is very smart. I think it should be regardless of your age. People die less this way. A year with less poer is not a big deal.
You could easily get your 400 restricted to pass 25kw, not even a big change to what it is now.
you need to learn to ride. Did you read the read this 1st thread above.
I bought a '68 volvo s121 amazon when I was sixteen. Was gonna build it all trick. I tore everything off, did random shit here and there, started re-upholstering the door panels while the car had no engine or much else in it. I was doing it wrong. Your project thread is like me at 16. You are not proceeding in a smart way and you are setting yourself for a failure.
btw. If you need a volvo roller body I have one for sale... Still have it. It will never be a car though.