Can the heir to the British throne marry outside the Anglican Communion? (a non-Chris

We know that the heir is prohibited from marrying a Catholic. But does the prohibition extend to members of other faiths, including non-Christian faiths?

No. Everybody in the Royal Family must marry a Protestant. A Catholic, Muslim, or Jew won't be and will never be accepted into the Royal Family.

No, he / she cannot. At least if they want to remain in the line of succession.

No...that is their one true cast in concrete rule. Whether King or Queen...in England they are head of the Church. No papery or other deities allowed.

By law, they are free to marry any religion except Roman Catholic. In actual practice, the situation has never come up, so it remains to be seen.