Per your previous:
There are two separate copies of the software on the unit. Under User, there are folders named PRG0 and PRG1. If your unit has never been updated, they are both identical. Updating to v6 should of overwritten only one of them. The boot loader chooses which one to run using the presence or absence of a file in USER called PRG.FLG. If this file doesn't exist, the loader uses the files in PRG0. If it does exist, it uses PRG1.
Am I supposed to go into the PRG0 and PRG1 folders and look for PRG.FLG files?
No, if present it should be a file in the USER folder. You seem to be using terminology in a non-standard way, and it is confusing the situation. A folder (also called a directory on many computer systems) contains zero or more files or other folders. A file can be anything that you want. It can be empty or contain binary data, text, music, pictures, or anything else that needs to be kept.
So if there was no file called PRG.FLG in USER (which also contains the folders PRG0, PRG1, and some others), you need to copy the one from your SD into the USER folder on the AVIC. That may be what you did, but from your description I couldn't tell.
After that is done, remove the SD and restart your unit. It should load normally. Then, go into Settings/System Settings/System Information, and see what the version is for Application.
Also check what your Bluetooth version is. I don't remember if it is on that screen, you my have to go into Bluetooth Settings.