Oppo F9 has a dual rear camera set up, 16MP and 2MP. The main 16MP rear camera has an aperture of f/1.8 while the second 2MP camera has an aperture of f/2.4.
Yes, Oppo F9 does have the OTG support.
No. Oppo F9 does not have the IR sensor.
Yes, Oppo F9 does have the MicroSD card slot. You can expand memory up to 256GB.
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.