metal gear story help

hey i just finished mgs and ive started mgs2 and ive got a couple of questions.

first of all what happened with otacon? why is he now working with snake on the tanker? (basicly what this is saying is what happened between mgs and mgs2?)

and second wheres liquid? he died in mgs from foxdie and yet i see him in all of the mgs4 previews. (if anything happens in mgs2 that will answer that pleese just say that ill find out.

oh and dont give me none of these wikipedia links just tell me with a simple answer.

Thanks