Interesting.
Now, again, I know little about Islamic history, and less about history of East Asia at around the time of the expansion of Islam, but I was curious as to what a Muslim China would look like. My impression is that missionaries for the religion first had a significant presence in the country at around the same time that Manichaeism and Nestorian Christianity arrived, but that these were all faiths that the Tang Dynasty sought to purge from their realm. My other impression is that Buddhism had a distinct advantage over the Abrahamic religions in appealing to the Chinese in that it was more open to syncretization with the country’s folk religions. Therefore, while it is possible to imagine a world where Christianity or Islam makes serious inroads in China, there would likely have to be significant concessions made to local customs. I vaguely recall threads discussing the possibility of a Christian China were folks have pointed out that Jesuit missionaries asked their superiors to allow them to accommodate the veneration of ancestors as practiced by the Chinese.
There were no missionaries. Islam generally does not spread in this manner; at least not the Sunni variety at the time period. Islam spread to China via intermarriage and trade ties, not through overt missionary ventures. At least among the Hui. For the Turkic populaces, these areas are Muslim prior to Chinese occupation.
Islam does not permit the practice of veneration of ancestors. At least generally. In the case of the Jesuits, they have flexibility regarding their theological principles on this matter; Sunni Muslim legal jurists do not. There is more of an argument whether one can even keep photographs, portraits and so forth of family members who have been made deceased. Much less veneration of ancestors.
Frankly, I feel that Islam could conquer Europe near totally, America, Africa mostly, Central Asia, Siberia, Mongolia, Manchuria, Indonesia, more of Hindustan (possibly, Vietnam, Burma, Siam, etc....
However, a total conversion of Hindustan or a majority, is most likely ASB. Likewise, a Muslim conquest of China is improbable without a Muslim steppe invasion of China (such as Islamic Qhara-Qhitan). As such, these areas would, alongside Japan remain non Islamic. Of a population of 7 billion people, having approximately 2-3billion non Muslim and the other 4-5 billion, is a wank of extreme proportions.