some of those are hard, if a trick could be explained for "envelope challenge" thad be much appreciated
Most puzzle cache owners are willing to give hints for their caches; they actually do want people to find them. I've never asked the owner of
Envelopes for a hint, but I'm pretty sure he's a reasonable guy. If you email him and tell him what you've figured out so far, he'll probably either confirm that your reasoning is OK and give you a hint about what to do next, or tell you where you've made a mistake.