Is it obligatory or an act of Sunnah to perform Iqamah before the prescribed Salah? What about performing it before the supererogatory Salah?
Like Adhan (call to Prayer), performing Iqamah before the five prescribed Salahs is a collective obligation. Iqamah is not required for supererogatory Salah.
What about calling to prayer before the due time of Salah?
Fifteen minutes later, the due time is affirmed. He then did Iqamah and performed Salah?
The Salah performed is valid. However, performing Adhan before the due time of Salah purposefully is a misdeed. A doer should repent and ask for Allah's forgiveness. Moreover, the Adhan should have been done again at the due time of Salah to let people who heard the first Adhan know of the mistake that occurred.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.