Vivo Y81i comes with 5V / 1A charger. It does not support the fast charging.
Yes, Vivo Y81i does support GPS.
You can record up to 1080p resolution videos on Vivo Y81i. You cannot record 4K videos via Vivo Y81i.
No. Vivo Y81i does not have the fingerprint scanner but it does support the face unlock.
Vivo Y81i has 2GB RAM of LPDDR3 type.