what the description says
I'm not sure. i guess just at a few random times. i remember hearing about them having like 300 morphing potions for just one neopoint at a secret time on a secret day, but i may be wrong.
You have to do an extremely rare Fountain faerie quest.
Here and there, but it is very hard to find them and they are super expensive.
The can be bought from the pharmacy in the main neopets shops. They can also be bought from users shops.
It is a battle dome item but is one use and doesn't do a lot of damage on your opponent.