Apple blossoms, as do the seeds and leaves, contain hydrocyanic acid (cyanide) ... however, people are known to use those blossoms (and others with the same chemical such as cherry blossoms etc) for making tea, steeped into vodka, and eaten.
Personally, I would not use those blossoms for wine.
Dandelions and roses are very different than stone and seeded fruit (which also contains the chemical).
If you decide to do it anyway, I'd do a lot of research first.
Often the "agricultural extension" departments of major universities (such as Michigan State University, etc) have data like that. You might check with an educational institution.