Here's what I've done so far:
1. Made sure GUPDATE.GCD was not in my device - GARMIN/system - okay
2. Formatted a 1.8Gb sd card
3. Downloaded the RAR file used WINRAR to extract and send it ti the sd card.
Made sure the 2689 was OFF, not on standby. Inserted card and turned it on.
4. When it had rebooted, I removed the sd card and checked it's contents on my pc. I looked in GARMIN\Updater\1948 and opened the file 'update.log'
5. It looked exactly as the spoiler showed.
6. I looked in my Settings>Device>About and it showed Software version 8.21!!!!!
Then I read the edit comment and inserted the line 'rrgn,154,2:/Backup/154_BKP.bin' as the second line (no Parsing starter) and repeated the reboot.
7. Now I'm back to Software version 8.20 !!
8. I'll delete my new line 2 and see.

Repeated the whole process, correctly this time. My 'update.log' file is as shown in the spoiler. my software is still 8.2 and 'can't unlock maps'
BUT, when I open the Garmin\device.xml it shows software 8.21.
G