Yes, toomanyitems does not require modloader.
yes
any will load mods onto minecraft but the better operating system the more mods you can have
yes, you can download mods easily on skydaz.com
No, Minecraft mods do not cost money, and are completely free of charge. I have never ran across any mods that require you to pay. In the related links below is a rather extensive list of mods, in the official forum for Minecraft. If you really enjoy the mods, in the thread, some mod makers provide a donate button. OptiFine specifically will award you for donating by giving you an OptiFine cape, visible only to other OptiFine users!
Minecraft is continually being updated with new features and bugfixes. These updates are downloaded from the launcher and are free, there is no 'paid DLC' like you get in games like Skyrim for example. Minecraft also has many user-made mods which add even more content. These mods are also free.
No, you can't.
fly mod
Check the forums for your other mods to see what mods they are compatible with.
There are none, the Xbox 360 edition does not yet contain any mods.
yes
No minecraft mods don't cost any money but it sometimes may be a project to get them.
Not yet but there is one that is kind of good. It tells you how to craft stuff