TdZ - Registration

I missed to register before Stage 1, but joined and completed stage1 yesterday.
do I have to register now or only joining the orher stages?

You have to register for the Tour for a ride to count.

how do I count afterwards my already finished stage, because of didn´t register in advance?

Gotta do it again if you hadn’t registered. You can do a short one though if you have bad memories of the effort.