If I have an apple allergy, does that mean i'd also be allergic to apple cider?

Likely yes. If you have an allergy to apples, you likely have an allergy to products that also contain apples, like apple cider, apple juice, apple pie, etc. If you have a bad allergy to something, you should get tested to see how bad it is, because it could be serious, and you should try to avoid anything that could have even traces of it.