Question

Who was the first imam in madina as imam for the first prayer(namaskaram)?

Answer 1

The Holy Prophet (PBUH) migrated to Medinah from Mecca.
He stopped at Qaba on the way and stayed there for some time.
During his stay in Qaba he commissioned the construction of a mosque.

On reaching Medinah he built Al-Masjid an-Nabawi. This was the first mosque in Medinah and is the second holiest site for Muslims.

He led the prayers himself as the Imam at this mosque, thus he was the first Imam for prayers in Madinah.