Can only stablecoins of type B) be on multiple blockchains?
Or can also stablecoins of type A) be on multible blockchains?
I'm not a coding expert, so my answer is it depends on how the architecture has the willingness and ability to develop code. Most stable coins run on smart contract based blockchains because (I think) it is more efficient in some ways, or algorithmic stablecoins like Terra UST also have their own blockchain so they are not affected by external network interference.
If you mean one brand of stable coin has both types, I don't think that's possible.