You should be OK. I'd just take it easy introducing the BP. Maybe every night or other night to start with. You might find that only night time aplication is neded. (Like me)

You'll most likely experience the usual SEs like drying but you should be in a good place to deal with it as adapalene gel can be pretty drying from memory. Make sure to moisturise well. I find a heavier moisturiser at the beginning is better than what you might end up using in the long run once you skin adjusts.

It should be fine. There is a medication (Epiduo) that is a combination of adapalene and benzoyl peroxide so they can work with each other. Often Dermatologists will prescribe using adapalene at night and then a benzoyl peroxide product in the morning. As with anything new it's probably a good idea to ease into it maybe testing things out on just one area of your face for a few weeks or using the benzoyl peroxide every other day or every third day for a few weeks. If you have been using the adapalene for a year already I would not completely stop using it though because you would have already gone through any initial breakouts with it and you are only getting the benefits by now. I would use the adapalene one night and then benzoyl peroxide the next on and off.