Old Etat de lieux, modifications and income cadastrale

Good morning dear community,
I recently won an auction through biddit.be, and after reviewing the apartment and all the documents, I have a few 'on point' questions. I would highly appreciate your input if you have knowledge about them. preferably hare a link where I can read more?
here they are:
1. Current contract is from 2007. In the note of sale, it was saying the ap is sold 'as it is'. I did receive from the notary a 17 page Etat de lieu. Is it still valid? Can I still call in an expert and assess the place after the renter moves out? I believe I am entitled to some compensation, as the ap is not in best shape.
2. The underground garage has the possibility to be closed with a gate, as the place is between 2 walls. Do I need special permission from the syndic, in order to install the gate? How about a power outlet?
3. If I want to remove some non-structural walls, that form a hallway, do I need permission from the Cadaster, or Commune? Do I need to inform someone, or get an expert to evaluate?

Any ideas on these topics are valuable to me. Thanks in advance