Never mind, i just separated the board to check if U3300 or Q3350 have any short (bridge) underneath or if it's broken, only to find out there's a bump of copper on the corner of U3300.[br]
Then i found out that the bump is exactly underneath the screw hole, like, man...
After i found out about it, i quickly looked at the other screw hole and... yes, it has a bump too.
The previous owner or 'repair technician' must have really tightened the super long screw until it punched right through the bottom side of the board. Guess I'll have to call it a day.
I wonder if this severe screw hole damage will fry the SOC or NAND after i plugged in 4v on battery connector to find the short.