i dont think they need to be able to do much for pre-school do they? if they are potty trained then hopefully they can pull down and up their own pants/trousers!
with regards to drinking i am sure mine could all drink from a cup at that age and re using cuttlery we never taught ours to do it but they always had it on their highchair, we did blw so lots of eating with fingers, my youngest is 17mths and uses a combination of fingers and a fork/spoon, if its something she can stab with the fork easily like pasta ie penne then she will use hte fork, if its not fingers all the way she isnt too good at using the spoon, scoops it up but tends to tip it off before it gets to her mouth! very common i think.
sitting at the table, well she is in a highchair for meals but at a toddler group i go to they have snack time and all the little ones sit round a table with breadsticks, and a drink etc she does it as all the others do, doesnt always stay up at the table mind but she will sit in a chair at the table.
re mess, well depending on the meal she can make a whole heap of mess, we had spaghetti bolognaise the other night i sat her in her highchair in just her nappy! she was covered the long spaghetti is harder for her to eat obviously despite me chopping it up and she ate mainly wiht her hands, but she loved it, i just cleaned her up with a flannel afterwards. some meals she makes hardly any mess at all, so its very variable.
my ds4 is at pre-school he now recognises his name, def learnt that from pre-school and he knows which coat and bag etc are his and lunch box/ drinks bottle, when he gets to pre-school he goes in, takes his lunch box to the lady stood by the kitchen door and then puts his drinks bottle on the little table they have for them, this again is something he has learnt whilst there, but they all do it so they pick it up quickly ie a parent or helper shows them a few times and its amazing what they learn in a short space of time :) ditto at the end of the day when i collect him, he will be sat on the mat and when i go in he knows to go and get his lunch box, drinks bottle and bag etc plus any pictures etc that he has made that day to bring home.
my ds4 started just after his 3rd bday and he wasnt potty trained, it wasnt an issue, he only did half days at first, then once he was potty trained, 3yrs 4mthsish? he started full days, only 2 days a week, i tihnk that is plenty for that age (it was for my children anyway)
its also helpful if they can get their shoes, hats etc on and off, and coats tho thats tricky for many at that age, there is NO pressure to do any of this tho, gentle encouragement and help and lots of praise etc, but def no making an issue of it if they cant do anything, they just get offered help. i guess it all varies according to the pre-school, when my ds2 was little i purposefully didnt use one pre-school as they seemed VERY strict and insistent on the children being very independent to the point that it seemed very regimented etc and the staff seemed harsh ( i spent a morning there with my ds2) anyway i didnt warm to the place so he didnt go! never known another one be like that tho :)