What are with these same mod titles but different versions? SOme go to 1.8? Does this mean you need the mods 1.1-1.7 to use 1.8?
No this simply means that there are new features included. Many programs use this system. A new version is released when something new is added into the Mod.
If you need the earlier mods to play a new one is up to who makes the mod. Though this usually is not the case.
For the two major mods, cr0nix's and warlords, you do need the earlier versions.