Nope, everything on your profile for TF2 (backpack/controls etc...) is kept online.
Weapons cannot be "leveled up" in TF2
if you want to get the scout weapons eg. do achevments
You get metal in TF2 either by trading or by crafting down the weapons you find
No, since your achievements are stored inside Steam Cloud, otherwise people could just edit the relevant file(s) to get all the achievements.
Strange weapons are obtained from unboxable crates.
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.
no
download them from garrysmod.org
You can't pick up weapons. The weapon you wish to use must be in your inventory and then you can equip it.
Nope, sorry.
Nothing happens, that information is saved to the steam servers. In other words they'll be there when you re-install
No, because robots are AI and strange weapons only track player kills.