If long battery life is your only concern, ( I mean, really long battery life) then, go for Moto Z play. Otherwise, in all other aspects, its OP3. And with OP3 too, you’ll get a full day’s battery on a single charge and that’s good enough for me.
Under 20k INR, I would suggest mi5 or the Zuk Z2. You can also go for J7 prime, if you want something of a branded device. Or the Sony XA, and the XA ultra.