Harry Potter and the Prisoner of Azkaban question

I've always wondered something and can't remember it ever getting explained in the series. So to teach Harry how to fight dementors with the Patronus Charm Lupin uses a boggart because he knows it will take the shape of a dementor when it sees Harry. Now my problem is that when it transforms it has the exact same effect on Harry that a real dementor does, and Lupin even gives Harry chocolate after the lesson which is used to reverse the symptoms that come from being in close proximity to a dementor. Does that mean that the boggart gains the abilities of whatever form it takes? Earlier in the book Ron made a boggart transform into a giant spider lile Aragog, which is extrememly venomous. If it had bitten a student would that student have been injected with venom? Also Neville turns the boggart into Professor Snape, who draws his wand. What that made me think was if Harry had turned the boggart into Voldemort like Lupin had feared would it have been able to draw a wand and throw a killing curse at someone? Also one more thing, the boggart became a full moon for Lupin, and if the boggart has all the ability of whatever it becomes like with the dementor shouldn't that have forced Lupin to transform? Somebody help me out here because this has bugged me since high school and if Rowling explains it somewhere down the line and I missed it I really would like to know.