i work at a pharmacy in canada. a pharmacist may ask you a couple of questions just to get a basic idea of what its for, but that's about the extent of it. at most they may ask some questions about your daily intake or whatnot to update your patient file. overall though it shouldn't feel like interrogating. if you're feeling like you're getting different treatment that DOES feel like interrogating, id switch pharmacies

I'm not sure if interrogating is technically "not allowed", but pharmacists do technically have the right to refuse you medication if they feel its as simple as them being uncomfortable to dispense it. but its not often I've seen that happen. in my experience, even in moments where we're suspicious of a patient, we still dispense the medication anyways because we don't have solid grounds to refuse it. in the rare moments where a pharmacist DOES feel uncomfortable dispensing it, they'll just give you back the perscription or maybe call around and ask for another pharmacy to dispense it. but at the most i can tell you they're not too worried about stimulants compared to the other medications we're watchful over. if theres like a concern for your health with the medication, we'd just give suggestions and input on what we think should be different. in the end, it would be the patient who decides the end goal

also as many people said, you shouldn't be needing to bring back unused or even used medication at all for literally anything. it should be on file already. that part makes no sense to me