you tear off the prickly parts with your fingernails.
That's what my grandfather used to do. Can't just chop it off? :P
From the petals? How so?
You pick the petals from the wild roses and just mush them with sugar to a thick paste. Then off to the jar.
It is not eaten on its own. You can add some to tea to make it fragrant or to so jam. Mum normally mixes some with plum jam that she stuffs doughnuts with. It's amazing!
I found recipe in Polish: https://klaudynahebda.pl/konfitura-platkow-rozy-ucierana/
RE: Rosehips for the finches.