Muhammad started of Islam as God's religion and then made it his. You have been acting in the same manner. And Muhammad was a Muslim.
alleged stories of Islam says Prophet got first revelation when he was 40. Did he get circumcised when he was 40?
if Not he was Not Muslim.....Again Muhammad was not one guy.. one character, one personality,, Islam started either with Jewish sect or monotheistic Christian sect somewhere between Israel, Egypt and sand land. And the reason was to tell the folks Paul's Christian story was wrong and Christ was Not son of god but a messiah/prophet .. That is what it was to start with. all the way until Khadija died. That means first 10 years of Islam was nothing but
" preaching Arabian pagans and Christians, that Christ was not god or son of god" and signing Arabic songs telling stories from old testament in pagan temples and close by towns..
90% of present Islam what we see now or read in Quran/hadith comes from the last 10 years of alleged prophet Life after the death of his first wife Khadija.