Can a Purity ring be any ring or does it have to be a special ring?
yes if you wont A Purity ring can be whatever you want but most people like the idea of a cross or some kind of inscripting.
Can you take any ring and just call it a purity ring or does it have to be a specific kind like it has to have a cross on it?
I think that not every kind of ring can be called purity ring. ** Because there is no such thing as an official purity ring (as stated by the Church of England, I don't know about anywhere else), any ring can be taken and used as a purity ring. It's what you think is a purity ring, and what it means to you. Some prefer to have it engraved with a saying or something, but…
A Purity necklace is the same as a purity ring. The difference is it is just a necklace instead of a ring but it means the same thing. I have a purity necklace myself and if you are thinking about getting one it is a awesome thing to have. So like you can have a purity ring, purity necklace, purity bracelet any jewelry really it all means the same thing.