Hi everyone.

When a hack strike we can do a bunch of stuff and most of the time there is a "level" in the description, how can we improve that level?

You can't. This is basically because a defensive program forbids lvl 1 results. If the program is placed on the system you hack you'll only have acces to the results listed with a lvl >1.

Wait so we cannot abduct more than 1 sleeper at the time? How the Rapture succes is even achiavable then?

In case you hack enemy home system you can abduct multiple sleepers depending on their total number in hacked enemy empire.

Also you can try this in a system with 1 pop. Have to admidt I didn't get this one

I think you can also get this from invading a system and you get an option to retreave all sleepers. If the full population is sleepers you would get the achivement.