Yeah, they get confusing when they dont make significant differences in the naming conventions.
In the 9 series ones (referring to 9 series OS)
A, B are 2.0 - downloadable and non-downloadable
C, D are 2.5 - downloadable and non-downloadable
E, F are 3.0 - downloadable and non-downloadable
And the 10 or 20 before the letter signifies for sale or wap.
In the A and B series ones (referring to A and B series OS)
B is for sale games
C is for WAP only
E is for daily fee
[/size]And the B series ones[size=78%][/size] weren't developed for[size=78%][/size][size=78%] [/size][/size]2.0 or 2.5, only 3.0 lol.[size=78%]As far as jumper, there may be a version where the jumper is not needed but that's not intended, the jumper is only for an added step in write protection and write enabling.
Dave