Result: it's bricked and other people in some Brazilian forums have done the same mistake. I'm trying to help them.
If turned on normally it gets stuck in LG's logo screen. Hard factory reset using buttons or USB cable method doesn't solve the issue.
The user says he tried many ROMs (probably also L7 I ICS ROMs :x) and after installed some ROMs make white stripes appear in the screen and others will make the LG logo screen to blink.
If turned on with the right buttons to enter emergency I think it does normally.
LG Mobile Support Tool isn't able to recover it. It gets stuck in % / says unknown error.
Tried KDZ with PhoneMode Diag, Emergency and CS_Emergency, nothing will recover it. Attached is a screen of a failed try of putting the correct stock L7 II P715 firmware on it.
My idea: maybe we can recover it by flashing a custom recovery (via adb or something else that works in emergency or download mode) then he could flash anything in his phone including the correct kernel and ROM and everything should be fixed, but since unlocking the bootloader is a requirement (please correct me if I'm wrong) and it seems the only method of doing so requires a phone working normally it seems there's no solution.
The technicians from repair centers are noobs, they were unable to recover it (I think they don't even have a BOX for this device model) and blame things like the motherboard or screen.
Any help would be appreciated.