Coelacanth, You have a lot of confusions. First of all, please understand, Islam not established by Prophet Mohammed (SAW). Islam was introduced to the earth through the First Prophet Adam(AS) and passed through all of Almighty's Messengers/Prophets and finally reached to Prophet Mohammed(SAW). T
he teaching of First Prophet and the Last Prophet is the same. Pray To the Only One Almighty, Only Creator of universe. Nothing else.
Those Prophets/Messengers until Prophet Mohammed(SAW) was issued with certain objective to particular generation/community/region/period and all those instructions and teachings were supserseded by the revelation of The Holy Qur'an. The Almighty confirmed that the Revelation is full and final with the last verse of The Holy Qur'an and He will protect the revelation Himself from any modification/addition/delition which happened to His earleir revelations through the previous Prophets by their followers...
Islam means Believe and Pray to Only One Creator, Accept and follow His Prophets and Messengers. That is why Muslim is Accepting and loving all the Prophets and Messengers of Almighty.,