IME

1) Yes, unless you are on a long term stay or have an agreement stating otherwise. The definition of long term varies from one property to an other. IIRC, they wont change sheets unless you put the card on the bed or the towels unless they're in the bathtub.

2) ofc you can if you want, but I've always come back to clean dishes in the dishwasher at the end of the day if I happened to used any. On a recent trip to RI in YUL, there was a card saying they would only start the dishwasher if it was at least half full. I didn't use any dishes so I couldn't comment on that, and I've never seen that card anywhere else.

3) I've done fairly long lists before and they're good at getting what you asked for. In some cases, they have agreements with grocery stores and get good discounts on groceries. I've also gotten Marriott points for groceries as they put it on a Marriott bill ^. For transparency, they give you a copy of the grocery bill along with a copy of the grocery list.

4) Don't miss out on their weeknight receptions. Generally good dinner food and free booze. YMMV. They also let you bring breakfast to your room, and will pick up breakfast dishes during housekeeping.