7. Should I agree with another user’s ID if I don’t know what it is?
You should only add an ID or agree to an ID if you can independently verify that ID yourself. So if you do see that someone has added and ID to your observation, take a moment to do some research, either with a field guide, on iNaturalist itself, or elsewhere on the internet, before you decide to agree or not. You can also always ask the identifier how they reached their conclusion.
Even if you can’t finally decide either way, you’ll probably have learned something, and that’s why we’re all here. :-)