Its normally worth 1 scrap
Technically, no, not officially. There are skins that you can download to change the Rocket Launcher and/or the Greande Launcher.
About 0.33 to 0.66
About 1 or 2 reclaimed
none unless u buy a key
TF2 is free-to-play
A clean Backbiter's Billycock is worth 1.44 refined metal, according to backpack.tf
A fricken Scrap
You can't, but you can delete all your Achievements and start over.
Yes. TF2 is a GREAT game, and I recommend you "buy" it. TF2 is now free to Play.
No, TF2 is not playable on a phone
No you cannot trade weapons for beta tf2 to normal tf2. Beta Tf2 is considered to be a completely different game by steam. Therefore the two game's inventories are not compatible.
Whether or not you should sell your inventory is up to you; the question is whether or not it is worth anything.