There are 45 ranks, and there is sub-ranks for assault, engineer, support, and recon, but there are also 100 eagle ranks (colonel).
Colonel 100
you get it on level 34
Yes, you do.
Level 40
If you only have the demo of the game.
No
In Battlefield 3 online multiplayer, the player can unlock weapons and other gadets by gaining points. The "C-4 Explosives" unlock for the Support class is unlocked by gaining 4000 score as the Support class.
If you buy the game then there will be a code with it.
Once.
Yes, why would they not.
In Battlefield 3, the highest elevation in the game is on the map Damavand Peak, the altitude there is unknown. The highest altitude the player can achieve is approximately 1000 meters / 3281 feet in a jet aircraft on any map with jets.
You can get the UMP-45 at level 16 in Battlefield 3 on the Assault class. Other classes may work I am not sure on that though. So, just keep getting points and progressing in the game and you will get there.