The ps vita does charge via usb on a pc and such so long as you have the option enabled it is by default.
Ps vita usb cable not working.
Select supply power to usb ports select always from the menu on the right.
And when your ps4 not reading usb then you can t access files as well you can t transfer any data since this usb storage device can t be used by ps4.
As for that extra port its still just an accessory port that is iirc disabled in software and might even be disabled in hardware tho im not sure on that one.
Us the ps button or the o button to get.
The steps below walk you through charging in rest mode.
From the ps4 home screen go to settings power save settings.
So now the question is why ps4 can t read or recognize usb flash drive.
Leave it unplugged for at least 5 minutes and then plug it again.
I think the problem is not the usb cable but the battery.
Otg will not work cause iirc the usb controller chip in the vita does not support hub mode which is required for otg.
Something like that at least.
The issue is that tt isn t visible on the unit which is why people don t think it s actually charging when you use the supplied charger you will see the battery visual change to show that it s charging.
Try to charge it.