The Da’wah of the Prophet Muhammad , was not restricted to a particular time or place, rather it was a universal Da’wah; one to last until the end of time.
Allaah is the proper name of the One True God. Nothing else can be called Allaah. This term has no plural or gendfer, which shows its uniqueness when compared with the word ‘god’, that can be made plural, gods; or feminine, goddess. It is a known fact that every language has one or more terms that are used in reference to God and sometimes to lesser deities. This is not the case with Allaah.
The word "Muslim" means one who submits to the will of God. The first principle of Islam is known as the Shahaadah (Testimony of Faith), and is as follows:"There is no one worthy of worship except Allaah (God) and Muhammad is the Final Apostle (Messenger) of God.”
In a broader sense, anyone who willingly submits to the will of God is a Muslim. Thus, all the prophets preceding Prophet Muhammad, , are considered Muslims.
About Islam 
, was not restricted to a particular time or place, rather it was a universal Da’wah; one to last until the end of time.