Hidden charges at possession are the real deal-breaker

Greater Noida West mein Unnati Fortune World dekh raha hoon for a 3BHK upgrade. Currently in a 2BHK, so thinking if the price jump for a bigger place is really justified. I've been researching, and realized possession experience is critical. Log kehte hain actual possession date aur promised date mein bahut farak hota hai, especially with projects in this area. Kitna delay expect karna chahiye Unnati Fortune World se? Aur kya hidden charges aate hain at the very end? Suna hai PLC, parking, maintenance deposit jaise charges last minute pe maangte hain. Registry process kitna smooth tha for you all? Koi unofficial demands for OC or something? I'm trying to figure out the real total cost. Any tips on how to verify these things beforehand would be helpful. Hope this helps someone else also looking.