Garry's Mod Set-up Question

I read the FAQ and searched the forums, but I couldn’t find a definite answer. So here are my questions:

  1. Do I need to install any of the Source SDK’s (base or full) in addition to one of the Source games to run the latest Garry’s Mod?

  2. Can I run Garry’s Mod with just one of the Source games installed and no Source SDK’s installed?

  3. Can I run Garry’s Mod with just one of the Source SDK’s installed and no Source games installed?

  1. No
  2. Yes

I’m not sure about 3 though

  1. No, because you need a source game installed in order to install its SDK anyway