Yes, LG Q6 Plus does have the Corning Gorilla Glass.
No. LG Q6 Plus is not a waterproof device.
Yes, LG Q6 Plus does have the face recognition. You do not even require to power up your phone. It's camera automatically detects your face and unlocks the phone more quickly than typing, drawing or fingerprinting.
No. You cannot change the color of the notification light in LG Q6 Plus.