Garry's Mod is only for Valve-released games, so no.
Buy Garry's mod 10 off of steam.
Yes, garry's mod will work with portal and you will have all the HL2 stuff.
technically yes, there were a few updates it is still called Garrys mod 10 though
Garry's Mod 10
It may work but it will be extremely slow and likely to crash a lot.
no because garrys mod requires that you have a game that uses the source engine
Garry's Mod has now updated and includes all features of 13 Beta
Garry's mod tornado
Steam
yes
You Do Not Get Garrys Mod Serials, You Buy it Off Of Steam Which can be found at steampowered.com its usually about 21 United States Dollars
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