Are the MVP achievements in Battlefield 3 stacked?

There are 3 MVP achievements in Battlefield 3, They are:

Most Valuable Player
Finish as MVP in a ranked match

1st Loser
Finish as 2nd MVP in a ranked match

It's better than nothing!
Finish as 3rd MVP in a ranked match

If I unlocked the "Most valuable player" achievement, having not unlocked the other two, will the other two unlock as well?

No they will not. You must specifically finish as the MVP that the achievement requires you to.

Finishing as MVP 1 will not unlock the achievements for MVP 2 or 3, you must finish as MVP 2 or 3 to unlock those achievements.

No. They are not actually achievements (as such). They are more a recognition of your work on the field of battle and contribution to the teams performance (for the most part). For this reason, they award different amounts if you win one. (with MVP = 500, MVP2 = 400 and MVP3 = 300).

This is why they are classified as Medals and Badges, not achievements.

However, Badges do stack (I know this as I have 4 Resupply Badges. More ammo, anyone...?)