If you leave a tank full in it will protect the inside of the tank......BUT it will go stale and the car will run Badly until its used up [never drive it hard with stale petrol!!]

To be honest I store my car every winter and for the sake of 3/4 months I really wouldn't worry about it too much

The inside of you fuel tank isn't going to rust.....your cylinder bores aren't going to rust and your engine sieze...your tyres aren't going to fuck up.

All I do every year is make sure the underside of the car is dry when I put it away [usually by driving the car really hard to get the exhaust up to temp which helps dry the underside]. Uncouple the battery, leave no fuel in it, make sure the tyres are at correct pressure and leave a window open a bit. I also start it at least every 2 months.