Noida 3BHK upgrade: What hidden costs should I watch out for?

My current 2BHK is feeling too small for the kids, so we're finally looking to upgrade to a 3BHK in Noida. Asgerpur mein SS Buildcon ka ek project dekh raha hoon. Hidden charges se bahut darr lagta hai, possession ke time kya kya nikal aata hai? Aur payment plan mein CLP (Construction Linked Plan) ya down payment, kaunsa better hai for end-users? Koi experience share kar sakta hai?