1) The murials started to decompose once they got there - and there wasn't a lot of writing for him to translate? Can't remember
2) Janek was the captain, vickers was the mission commander (think Burke / Gorman in Aliens)
3) Presumably they were alien slime monsters / squid huggers or something - may not register on instruments or something
4) Cos it was decapitated and that's gross
5) Same as Alien - Ash knew - but how?
Clearly the Company knows stuff - I mean, they knew there'd be engineers there - Weyland himself came on the mission with that express purpose.
6) He was speaking with SOMEONE with that helmet / face plate thing - wasn't necessarily Weyland, either, cos he could have just visited him in his room. Yutani?
7) metal irises?
8) not sure on this one.
9) well to be fair they weren't expecting what they found... maybe they did? also it'd blow the cover.
10) yeah.. that was teh dumb.