Yes, Samsung Galaxy J4 does have the 3.5 mm headphone jack.
Yes, Samsung Galaxy J4 does come with the headphone in the box.
No. Samsung Galaxy J4 does not have the NFC support.
No. You cannot record 4K videos with Samsung Galaxy J4. You can record videos up to Full HD resolution. It has a 13MP rear camera.
Yes, Samsung Galaxy J4 does have the front camera flash.
Very Nice Display And Overall A Good Phone
The display is very nice. It beats almost all phones while using under direct sunlight. It has lot of other features also like power saving mode, front camera flash, etc.
I suggest this phone.