3 years of OC delay – my upgrade fear in Sohna

3 saal ho gaye, abhi tak OC nahi mila for my current 2BHK in Sohna. Builder ne toh thaka diya hai. Ab I'm thinking of upgrading to a 3BHK, maybe around ₹1.5 Cr budget, eyeing projects like Tata Housing's Paramount Luxury Floor 63A. But builder ka legal track record kaise check karein? RERA complaints ka kya fayda hota hai, is it actually effective ya bas paperwork hai? Bohot darr lag raha hai phir se phasne se.