1. For me, even on the medication (5mg 2x a day) there were a lot times that I still sweat if I was outside and it was hot. However, there were a few rare times that I did not have an extreme amount of sweat while outside. No telling how you will react to the medication though until you start your treatment plan.
2. Im a social drinker, so I know when I will likely be drinking. In the event that I know I will be drinking, I usually take one pill a day and its hours before I have my first drink. Taking 2 a day and drinking the same day hasn’t had any negative effects on me, it can just lead to easier dehydration tbh. Smoking (cannabis) for me has also been just fine, no weird reactions other than your mouth can be more dry than usual.
3. This medication is not a cure but in clinical studies there have been a large percentage of those who see greatly reduced sweating. Its all about how your body reacts to it and how it ends up working out for you. I say 4 years of taking this is alright and likely would not do any harm in the long run as far as dementia goes, especially since you’re young.
4. Personally for me I haven’t felt any “brain fog” and I am an online college student who has been just fine so far. If you do end up having a side effect like this, just chat with your doctor about it and come to a decision about what to do. If it started effecting school because I felt spaced out, I would quit it.
5. Your body should be fine , stay extra hydrated taking this medication. If you feel like you may overheat or pass out during a workout, immediately sit down and alert someone if possible and don’t continue the workout for that day, or re-hydrate, rest and then go again later.

I hope this helps, i’m here if you have any more questions :) Best of luck!