questions in Half-Life

I got this achievement before even starting up Half-life 2 episode 2, Can anybody tell me what this is?

anyone wanna play original half life?(hl 1)

Do you want to see fan made headcrabs made by me?

What's the best Half-Life game?

If you were a headcrab, which headcrab would you be

If you were a headcrab zombie, what would you be?