you might not need to cut your stock studs depending on how much space you have in the back of your alloy wheels. i would get "hubcentric" spacers like these. i'm not sure the diameter of the RAV4 though.
Yep, you need hubcentric spacers, as it's what centers and locates the wheel.
But yes, the nuts that come with the spacers locate them onto your hubs, with your existing nuts holding your wheels onto the spacer.
You'd need to look at the rear of your alloys, but they usually have a void where they would conveniently go over the nuts/studs in the spacers. There is only one way to make sure they fit though, try one.