Planning H2 purchase

[Scarsman]

I am planning to get an H2 probably within the next few months. I have been reading on here for awhile learning what I can, but I have a few questions I have not found good answers too yet.

1.
Are there different gear ratios? I found an old post saying at that time they were all 4.11, but have they added anything different?

2.
Are there any years that stand out as being better? I understand that they got more power in 2008, and a 6spd tranny in '08 or '09?

3.
I looked at a 2005, and above the 4X4 buttons there was a button with a pic of an axle with an X on the diff and a little padlock. Is this an electric rear locker? And do any have a front locker? The dealer had no clue about Hummers at all.

4.
What does the adventure package add? Is the air ride part of that? I will be using it offroad.

I will probably have more questons later, but I have been scouring the search function to try to keep them to a minimum. Thanks!