Yes, Oppo A5s does have a dedicated memory card slot. You can use up to 256GB MicroSD card in it. Besides, Oppo A5s also has OTG support.
Yes, Oppo A5s does have the OTG support.
No. Oppo A5s does have the fingerprint scanner but it is not the in-display fingerprint scanner. It is placed on the back side of the mobile.
No. Oppo A5s does not have the IR (Infrared) sensor.