Yes, Oppo F9 does have the MicroSD card slot. You can expand memory up to 256GB.
Yes, Oppo F9 does have the double channel LPDDR4X type of RAM.
Oppo F9 has the aperture of f/2.0 for its 16MP front camera.
No. Oppo F9 does not have the front camera flash but it does have the display screen flash for the 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.