No. Oppo A5s is not a water-resistant mobile phone.
Yes, Oppo A5s has a dual rear camera set up. The primary rear camera has a resolution of 13MP while the secondary rear camera is of 2MP resolution.
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.
No. Oppo A5s does not have the IR (Infrared) sensor.