Vivo Y95 does have the OTG support.
No. Vivo Y95 is not a waterproof mobile phone.
Vivo Y95 has LPDDR3 type 4GB RAM. It's single-channel RAM.
No. Vivo Y95 does not have the front camera flash but it does have the display screen flash.
Yes, Vivo Y95 does support face unlock. It also has a fingerprint scanner.