Muslims believe that God sent messengers all preaching an identical theology: worship Him alone, do good deeds, stay away from evil, and repent to God. The line of Prophets began with Adam (peace be upon him), continued through Abraham, Noah, Moses, Jesus, and all the others in between and ended with Muhammad (peace be upon them all). All of these prophets were "Muslims" in the sense that they submitted to God. Some of these messengers came with Law (and some followed the Law of previous messengers). This Law differed from one period to another, and from one people to another people. In their time and place, that was "Islam." The final message and Law is the proper noun Islam.
Your question deals with the differences in Law - Muslims don't claim that the rituals and specific details of the Law were the same since the beginning of mankind. Messengers which were sent with Law all had different details (dietary, worship, etc.). Someone who lived in the time of one of those Messengers was being a "Muslim" when they followed the applicable Law. Today you are Muslim if you follow what Muhammad (pbuh) was sent with.
As for theology, ALL prior faiths and revealed religions are distinctively "Muslim" in nature. They all call to worship of one God (or at least, we believe they did). Judaism is still strictly monotheistic and forbids idol worship. This is not necessarily distinctive to Muslims, but it is distinctive in the sense that it originated from the One God.