For (1), back when I was shopping around for insurance for a long trip which included a high-altitude trek in Nepal, most plans had some sort of altitude restriction in the fine print (though I don't remember what it typically was), or sometimes a very aggressive definition of "mountaineering". If I remember correctly some of them even offered an extra paid option to ease the restrictions. But I did manage to find a plan without such restrictions (it was Cigna, no idea whether their plan details are still the same). But short-trip plans may be less restrictive, I was only looking at long-term plans (i.e. travelling around a year).
As for (2), I don't know for sure, but I'm guessing you can find a plan that would only exclude illegal drugs. So if you manage to find such a plan, if the substance you're consuming is legal where you're consuming it, I don't think you should have a problem. But this is just my guess, I haven't actually tried finding such plans myself.