I think the problem is not the usb cable but the battery.
Ps vita usb cable not working.
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.
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.
The steps below walk you through charging in rest mode.
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.
Turn vita on and plug in the usb cable go to content manager then copy content select pc then usb cable right click qcma in task bar and hit connect.
Leave it unplugged for at least 5 minutes and then plug it again.
Scroll and select set features available in rest mode.
Something like that at least.
Select supply power to usb ports select always from the menu on the right.
You could try to open your vita and unplug the battery from the board.
Otg will not work cause iirc the usb controller chip in the vita does not support hub mode which is required for otg.
Us the ps button or the o button to get.
The ps vita does charge via usb on a pc and such so long as you have the option enabled it is by default.