Is it permissible for the Imam to lead people in prayer while sitting on a chair, performing the pillars of prayer—standing, bowing, and prostrating—while seated? And would the blessing be lost for the congregants who complete the prayer fully behind him?

It is permissible for the Imam to lead the prayer while sitting or standing. The manner of prayer for the congregants (Ma'moomoon) differs based on the Imam's condition:

1. If the Imam begins the prayer sitting: The congregants pray behind him sitting, based on the Prophet's (peace be upon him) saying: "Indeed, the Imam is appointed to be followed. So if he prays sitting, then pray all of you sitting."

2. If the Imam begins the prayer standing but then becomes unable to stand: The congregants complete their prayer standing, as happened when Abu Bakr prayed standing, then the Prophet (peace be upon him) came and completed the prayer sitting while the congregants remained standing.