Is it sufficient to recite part of the the final Tashahhud in the prayer of greeting the mosque when the Iqamah is called, in order to join the Imam?

Praying upon the Prophet (peace and blessings be upon him) in the last tashahhud is a pillar of the prayer, according to the preponderant opinion. What suffices for it is to say: "Allahumma salli 'ala Muhammad (O Allah, send prayers upon Muhammad)." Anything more than that is a Sunnah. If the prayer is established while the worshipper is in the last tashahhud of a supererogatory prayer, he is not permitted to omit praying upon the Prophet. Rather, he should limit himself to what suffices, then conclude his prayer with the salutation to catch the opening takbir with the Imam. This way, he combines completing his prayer with catching the opening takbir.