New to thr launcher and have a few questions

[Qwertsy]

Hey guys. I have a couple questions that you guys could hopefully answer for me.

1) I understand the reason for not having an offline mode. So far since downloading the launcher and signing in with internet connection I have only been playing voltz. My apartment doesn't have internet and I've been playing voltz just fine, however when I tried to switch modpacks without internet it wouldn't let me. Am I only able to play the last modpack that I played while having internet connection?

2) Is there a way to add a single mod to a modpack? Or do I have to create my own modpack? If so, where are the mods located? (I've been unable to find them in the technic folder) This is basically railcraft added to voltz. So where would I go file wise to get all the mods from voltz and railcraft (which I'm pretty sure is in one or more of the other modpacks) to make my own pack.

3) Last question. Assuming I make my own pack (voltz + railcraft) am I safe to just copy my current save file of voltz to the new folder created by the technic launcher for my custom modpack?

Thanks for the help guys.