After my flight, I have an update regarding the special seat selection:
1)Before check-in: I could select the 1st/bulkhead row, but got an error message
2)Online check-in (48h ahead): Sucessfully selected the bulkhead row and travelled there.

Equipment: A320/A321 (Regional). The whole product is crappy, but I preferred the bulkhead, as I could press my feet against it, which allowed for a more varied seating position. I hope I find some time soon to post a trip report with some photos.