Does one realize the virtue of congregational prayer if one catches the last Tashahhud with the Imam, or is it better to wait for another congregation, and is the reward for praying within the preferred time like the reward for praying with the Imam at the beginning of the time?

Performing prayers at the beginning of their prescribed time is among the best deeds. Performing the obligatory congregational prayer is a duty for men, and it is not permissible to abstain from it except for a legitimate excuse. If the Imam delays the prayer until the end of its time, the worshiper must pray it at the beginning of its time, then repeat it with the Imam, and it will be counted for him as a supererogatory prayer.