Prophets may differ in the number of marriages and other personal customs, and their communities may also have differing practical laws. An audience attached to existing arrangements can mistake such differences for a break from religion itself.
Yet that conclusion depends on a further premise: that authentic prophethood requires every detailed rule to remain identical forever. That premise must be argued, not assumed.
For example, if prophetic marital practice or a communal rule differs, the difference alone does not decide which revelation is genuine. One must consider the addressees and purposes and separately evaluate the evidence for the new prophetic claim. Divergence in legal detail need not imply disagreement in the core of faith.