Apple Cider

my dog is having ear irriation and i have been reading that apple cider vinegar works best to clean the ears out and kill yeast and bacteria.
how much of it should i use and how should i put it in her ear?
will the vinegar burn her or cause her harm in any way?

also, can i use mineral oil directly after to soothe her ears?

I have an acre where I already planted a Pink Lady and Fuji apple tree. I plan to get a Golden Russet to help pollinate the Pink Lady and start making my own hard cider. What yeast would I want to use for a fairly sweet result? Recommendations for blends of these apple varieties or others?

I was talking to a friend one day who had expired apple cider in their refrigerator. They said that apple cider actually doesnt go bad but ferments, becomes alcoholic, is this actually true? Can apple cider just become hard from sitting around and not adding yeast/sugar to it?

I’m just curious can one make apple cider from juice or is apple cider the product of pressing apples and then catching the liquid that runs off from the press afterwards? Also will fresh apple cider ferment on it’s own or does yeast need to be added to help the process along?

I’m kind of new to this hobby of cidermaking but I think it could be a very interesting and rewarding hobby.Thanks for any responses