Yes, Oppo F9 does have the GPS support.
No. Oppo F9 does not have the front camera flash but it does have the display screen flash for the front camera.
Yes, Oppo F9 does have the face unlock.
Oppo F9 has the aperture of f/2.0 for its 16MP front camera.
The most striking feature of the Oppo F9 is the big display with the waterdrop notch. It is well designed, delivers good battery life, and offers decent performance for the price.