What are the levels xp for each preview

The highest level you can obtain in Mass Effect 2 is level 30, it's no longer 60 as it was in Mass Effect 1 as they changed the way you level up in ME 2.

If you import a level 60 character from ME 1 for example, you will start out at level 5 in ME 2 and you will gain XP after each mission completed until you reach level 30; the limit.

Which is another change made from ME 1, in ME 2 you don't gain XP for each enemy killed or each crate/box/locker hacked/unlocked, instead you are only rewarded party XP at the end of each mission.

Anyone wanting to play hard mode and level up quick welcome to join each kill nets 100xp to 500 xp missions net 10,000 xp

You get XP for ALL modes! Just not the campaign. If you don't see it, it is still there. I haven't played in a while so I can't say for sure how much and where the XP bar is in each game type. But here is a calculator to figure out what you need to do, based
on what level you are and what the XP is that weekend.

http://www.gow2exp.com/m/calculator

Go here:
masseffect.wikia.com/.../Save_File_Transfer for a full list of what transfers from Mass Effect over to Mass Effect 2 with a imported character. Or read below

Character Stats and Levels

Due to several gameplay changes, your character's level and abilities will not transfer over to Mass Effect 2. However, the game will acknowledge your character's level and morality and adapt it in ways that map across to the new system as well. The higher
the level of the imported character, the greater the bonuses granted upon importing.

A portion of the character's Paragon/Renegade points (up to 190 each, which requires the bar(s) to be 50% full) are transferred over.

Importing a level 1 through level 49 character will grant 1,000 XP (the player starts at level 2), 20,000 credits, and 2,500 of each resource.

Importing a level 50 through level 59 character will grant 2,000 XP (the player starts at level 3), 30,000 credits, and 5,000 of each resource.

Importing a level 60 character will grant 4,000 XP (the player starts at level 5), 50,000 credits, and 10,000 of each resource.

Having the "Rich" achievement from Mass Effect will grant an additional 100,000 credits.

The import bonuses will stack with the Mass Effect 2 completion starting bonuses (200,000 credits and 50,000 of each resource).

during the last 2 dbl xp weekends i got through the full 55 levels each time