I need the answers to the following questions..

1. which sahabi is called imam ul ummat?
2. name the place where Hazrat Adam (AS) and Her Wife lie buried?
3. Which kalmas are recited at the time of nikah?
4. Who assasinated Hazrat Usmaan (RA)?
5. On which occasion Namaz was made obligatory?(i think Mirage)
6. The Holy Prophet (PBUH) led the prayers of all the Prophets, who performed the Azan?
7. Why no battle was fought in "Gazwa-e-Khandaq?

Plz reply..