Yes, Oppo A5s does have a 3.5mm headphone jack.
No. Oppo A5s does not have the front camera LED flash.
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.