Difficult isn't it, catering for one?
Recipes don't always work so well, they dry up or get overcooked or something's just not right. I've been known to have only eaten 2 different evening meals in a week 'cos you just have to keep eating it night after night (lol)!
Technically yes - but if you have to cook it in the oven, the cooking time may have to be reduced (but not necessarily so). Sometimes you just need to check the oven to make sure you don't overcook it.
You have to be careful because if you quarter everything you could for example be left with not enough oil for frying or a weird quantity of an ingredient to find (quarter of an onion, anyone?).
I think there's an old catering rule where the more people you're feeding the less amounts of each ingredient you need to cook with, and it works both ways so you'd be better off halving it and seeing how it is.