Why I can't do the required pit stop on first lap? Some tracks like Aston North and Westhill Reversed have pit entry after end of grid so I decided to pit immediatly from start (Aston N). I crossed start/finish line and made a normal pit stop but still when driving last lap I had 30sec penalty for too late pit stop.

I think that's clear if starting from the pits but when starting from grid and going to pit in the start of lap 1 that would be acceptable

In that case some people would have an advantage starting from the back.