What are the fundamental characteristics of Islam?

The fundamental characteristics of Islam are as follows:

1 – Islam addresses all ages and all people, the principles that Islam has brought meet all needs of the humanity.

This universal characteristic of Islam is indicated as follows in the Quran:

“We have not sent thee but as a (Messenger) to men, giving them Glad tidings, and warning them (against sin), but most men understand not.”  (Saba, 28).

“Say: "O men! I am sent unto YOU ALL, as the Messenger of Allah’.”  (al-Araf, 158).