When I when to Canada I ask for 7 days but I only stay 1 will this effect me negatively if I ever go back to Canada?
No. It should not make any difference at all. Except you are missing out on a longer visit to a great country!
So long as you are out inside seven days, that's fine.
Probably not. They keep a record of previous visits and can ask about them before allowing you another visit.
No. Expect questions as that's normal. As is walking you inside their Customs Station. Be frank. Answer as directed. Decline to offer opinions; stay factual.
its possible, if you only want to stay one day i would just ask for that