you can get stuck, yes.
apparently you can't put spoiler tags on these forums (rofl) so i edited the spoilers out.
anyway: i've had two instances of getting stuck in the first game. luckily i'm an 'often-saving' kind of guy, so i could just load a save-game from a few minutes ago.
It fell into the vase.
Most people get stuck in the first game because they ate all the apples, so don't!
i'm pretty sure apples keep spawning, actually.. the problem is that there are a lot of areas they can potentially spawn in, and only a limited amount (probably just one) can spawn at a time.
Even if you throw an item in a well or something, it'll just randomly appear elsewhere in the game. However, it is still very much possible to get stuck on the final island if you haven't brough the required items with you and you don't have an extra potion to get back to the mainland.
it's not possible to go back, even with a potion.
and i'm pretty sure not every
item can re-spawn. i would think twice before throwing an 'uncommon' item into the well.