I'm reviewing the minecraft mod website, and it states: Requirements: Minecraft Forge to install Minecraft Comes Alive mod. Also, the mod says Minecraft 1.7. Does that mean 1.7 is the minimum version, or it's the only version this mod will work with?
Minecraft Forge is in itself a mod which makes it easier to install other mods. It can sometimes be difficult to get working, but it's well worth giving it a go because it does make things a lot easier. There are instructions in the first half of the installing mods article, but if you get stuck at any point just give me a holler and I can help.
Yes when a mod mentions a specific version it means that it's made to run on that version. Sometimes it can mean a maximum version, so it will run on earlier versions, but it will never mean a minimum version. That's because each new Minecraft update adds new functionality or makes changes to the code that can interfere with the way the mod works. So you can't run 1.8 with any mod unless it says that it's compatible - since it's such a recent update it's unlikely that many (or any) mods have been updated to be compatible with it yet.
But that being said, it's super easy to run Minecraft in an earlier version. You don't need to reinstall it or anything like that, Minecraft has the ability to be run in almost any version each time you start the game. To do that you just need to change the version in the Profiles drop-down menu on the left when you start up - there are instructions in the How To Set Up A Version Profile article if you need them.
I hope that makes sense to you! Please do write back if you need help with anything, I know it can all be a bit confusing.