So, after my phone's been bricked for however long I can remember, I just took a chance by trying my hand at unbricking it.
Charged it first, but had to take a guess at how fully-charged it was because there was no indication. I then tried to flash it with firmware via Odin but it kept getting stuck at the hidden.img. I then flashed just the PIT file and then reflashed the firmware; worked this time around.
Rest of the day, it kept getting updates, to the point where it is running the latest Android version 4.1.2 - my S3 is not even running this version.