When you say that it is permissible to for a hanafi to act as imam when somebody taps his shoulder and makes him imam.

Your question raises a fundamental question and principle.%0D%0A%0D%0AAccording to the Hanafi Madhab, the Imaam and Muqtadie (follower) both must%0D%0Abe equals in Fardh Salaat. If the Imaam is performed, for example, Dhuhr%0D%0ASalaat, then the Muqtadi must also be performing the same Fardh Salaat. The%0D%0AMuqtadi cannot perform Esha Salaat, for example, behind the Imaam who is%0D%0Aperforming Dhuhr Salaat. However, a Muqtadie may follow the Imaam with the%0D%0Aintention of performing Nafl Salaat only in Dhuhr and Esha Salaats.%0D%0A%0D%0AReverting to your query, there is no congregational Salaat in Sunnah or Nafl%0D%0ASalat. If a person is performing Fardh Salaat by himself, and another person%0D%0Awishes to join him, with the intention of Fardh Salaat, he may do so. If%0D%0Athere are more than one person wishing to join the Imaam, then they will%0D%0Astand behind the Imaam or if there is no space, the Imaam will move forward.%0D%0AThey may indicate that to the Imaam by touching his shoulder.%0D%0A%0D%0AIt is compulsory to observe respect for the Khutbah even if you do not%0D%0Aunderstand it. We also wish to point out that the Khutbah should be in the%0D%0AArabic language.%0D%0A%0D%0Aand Allah Ta'ala Knows Best%0D%0A%0D%0AMufti Ebrahim Desai