Not specifically. You need a VALVE game to play Garry's Mod, one of which could be Half-Life 2.
No
Yes, garry's mod will work with portal and you will have all the HL2 stuff.
no because garrys mod requires that you have a game that uses the source engine
No, but you need .lua to make your own addons.
A computer that was bought at least after 2006 to run Half-Life 2 aka HL2
Yes, you can play online multiplayer.
No, there is not any games like gary's mod, but there is JBmod....a different version of garys mod, find it here. (see related link) It requires HL2 (Half life 2) so if you want another game like it, you have to buy HL2.
i want to play garrys mod no downloading and no buying
Buy Garry's mod 10 off of steam.
Eh? how is it possible to have HL2 installed on you computer but not on steam? The short answer is no. But you're welcome to try clicking "add a game in the bottom left corner of your library and adding half life 2 as a game.
goto droay two dirr
Yes because you can't play Garry's mod without steam.