Hey welcome to Vizzed!

Ok well
1. You get EXP from posting and the longer the post is, the more Exp you get and the more levels you go
2. Well it matters what exactly you want to do. Just delete the file that he was playing on so you can play it yourself or just because you stoped played the game

if to play yourself - Mattering on waht game it is but it most likely has a file saved on it so your bro could go on and keep on playing from where he left off you could try the Start or Menu button or something like that and should give you and option to delete. But then again all games are different and matters what game you are talking about

Not useing it - Go to your profile, then Gaming Profile, Click on the game you want to get rid of and it should bring you to the page where the game is provived and it should say "Sell game" in the top left cornor above the pictures of the game whci is about "Play now" options

3. Matters what the item is. But most likely after you purcuse it will automaticly be in use

If you have any more questions feel free to ask

Since youve said youve been here awhile i would say the next day after you post 10 posts since you have to be here 7 days and then have 10 posts to be a member

Im on a lot from Mon-Fri but havea lot to do the weekends

But with your question

You would have to buy it again. I just tryed it myself to double check. When you buy something after having something already in the slot that it will be put in it will disappear and be replaced by the iteam you bought.