1. What are Nirvanna ponies?
Ponies manufactured in basically any country other than Hong Kong or China. They'll have something different (or in some cases, nothing) stamped under one hoof. I'm pretty sure Italians are the most common Nirvanas, though even those aren't THAT common. Most others are very hard to find, especially in good shape!
2. How in the world do you all rehair those ponies? These CMs are just amazing!
3. For people who do customizing, how are you getting the glittery stuff off of the minis?
Not sure about these 2. Rehairing takes some skill that I don't currently posses!
4. I understand that the G1s are the original ponies (i.e. Cotton Candy and Lemon Drop--names that make me feel ultra-nostalgic lol) but what are the cut-off dates for the other generations?
What are these little mins considered?
There is some debate about what constitutes a certain generation of pony. Generally though, between the generations, there is a major design change for the whole line. As you see more and more different ponies, you'll learn that there are pretty significant differences between the 5 generations!
I'm assuming by "minis" you mean the blind bag ponies that are currently being produced? Those are G4. There were also similar miniatures during G3 and G3.5, though back then they were called the 'Ponyville' line (and mostly weren't sold in blind bags). They were released alongside the standard brushable ponies.
5. OMG--I never knew how many over-seas releases of our favorite ponies there are! How in the world do you guys keep up with all of them?
By sitting here and reading all these posts every day! =P We have fellow collectors all over the world! We all share what we find and what we know. =)