No. Samsung Galaxy A9 does not have the wireless charging support.
Yes, you can record slow-motion videos with Galaxy A9.
Yes, Samsung Galaxy A9 does have the Dolby ATMOS sound support.
Samsung Galaxy A9 does not have the front camera LED flash. But it has a display screen flash.
Yes, Samsung Galaxy A9 does have the 3.5 mm headphone jack.
With that said, we'd say that the Samsung Galaxy A9 (2018)'s four cameras don't amount to a whole lot just yet — you get a little versatility and they might occasionally come in handy, but we wouldn't call this an absolute must-have for photographers. Cameras aside, this is a competent phone that delivers strong performance and looks good doing it. If you're looking for a big, bold style statement, you've found one.
The Samsung Galaxy A9 (2018) is one of those rare devices that has a clear angle going for it, in a sea of smartphone sameness. In its case, that's both a blessing and a curse. It's very easy to focus on the world-first camera count achievement and simply stop there, either writing off the phone as a one trick pony or basing your opinion of it solely on its camera capabilities.