Why is my game crashing?

[Thesandbug]

So I've been noticing some things when playing the Half Life 2 beta on the Mega Build.

1. when I start up a game of the 2002 beta, It has only a few maps and the ones from the 2003 beta. It also says there is no map for d1_grarage when I press New Game in the console.

2. In the E3 2003 beta, When I try to use the Physgun, it just crashes my game. Same for the other guns.

3. "The Thing" Mod and "City 17" mod crash when I load into a game.

4. In the Half Life 2 2003 beta, if I kill a barnacle, it will crash the game if I try and load the next map up.

5. At the start of the nova prospekt map in the 2003 beta, When I load into the next map after the first map, The game crashes. I had to skip a section because of that. It only worked when I played the 2003 beta maps in the 2002 version. And that's about it. I'm hoping that someone can tell me how to fix this.

[Витой]

First of all as I can presume, you create multiplayer game to launch maps. It can be the root of your crashes problem.
Use console for launching maps instead of "Create Server" button.
Press ~ key and put
map ai_borealis
or any other map name in it, then press enter.

Secondly, to play 2002 maps you will need to download 2002 mappack.

[Thesandbug]

Oh ok. Thanks.

But I don't create multiplayer matches when I play. I hit new game. And what about the Mods? The only mods that work are the Air Exchange mod, the Town Mod, And the Borealis mod. Meanwhile, the Thing and City 17 mod do not work.
Edit: It worked but it still says that d1_garage_01_08 is an invalid map.