Power backup: full flat ya bas common areas?

Visited Prestige City last month, aur abhi bhi power backup ka doubt hai. Builder bol raha full flat backup, but parents bolte hain bas common area mein hi hota hai. Kya actual mein pura flat chalta hai backup pe? Yaar, Bengaluru mein itne power cuts hote hain. Water supply ka bhi tension hai, tanker dependency kitni hoti hai? First property hai, samajh nahi aa raha.