They dont tell you this if you own A13 and I did not know this either until recently.I had this phone for almost 3 years now and only found out recently it can play 4K movies.
The Catch:
Movie or Series has to be 8bit not 10bit and SDR not HDR
Frame rate needs to be 30 and under not higher(which is not a big deal since most movies are under 30fps anyways on all websites)
The Benifit of watching 4K content on this device is its 1080x2408 resolution the Horizontal resolution of 2408 pixels is higher than standard full hd.So watching 4K content makes use of your maximum phone resolution in comparison to standard 1080p
What happens is the 4K movie is downscaled to the phones native resolution of 1080x2408 pixels.
And note the device has a ppi(Pixels Per Ince) of 400 or so which makes for clear and verry detailed images thats why 4K on this display looks verry sharp.
You will not get the full benifit of watching a 4K video on a 4K screen but atleast its way better than watching the standard full HD which is limited to 1080x1920 pixels.
