Sorry I don't know about the apples, although I would think the owner would like to know his sheep have access to them.
I don't think though that sheep can eat too many gooseberries - our 'shy little forest creature' otherwise known as Balou the ancient Soay, has eaten her way through heavy crops of first of all Pax, a desert gooseberry, then through FIVE Invicta bushes which were all well laden. She's still going very strong
(We call her a shy little forest creature because she rustles away in the shrubbery and fruit cage helping herself to endless browsing, well camouflaged in there, and because she's definitely not a shy little creature
)
The sheep will also jump up to reach golden gages, and they strip the lower branches of those, so I imagine they eat plums as well.