no
as far as I am aware you do not have to pay for windows live messenger on your phone but you will have to pay for data if you go over your allowance.
i need product code for age of empires on windows live online games
No . It's free.
Most likely
Yes they should be able to.
If you buy something on XBox Live, games, add-ons, (everything except Avatar items) will be shared with all the profiles on that xbox, you can allways re-download it for free on any other xbox or location you are in, but will need to sing in in your windows live ID
No,it is free to use.
No, games for windows can only be played on a windows PC. It might be possible to buy the 360 version of a PC game though.
No
Microsoft's Windows Live lets you play cross platform games with Xbox players
Yes, they charge you $0.50 off your credit card! I don't know why, but they do.
No the Xbox live app on windows phones is able to link to an xbox 360 but it also has games that you can buy