The adhan and iqamah are only for the obligatory prayers. But for Tarawih, Witr and other optional (nafl) prayers, there is no adhan or iqamah.

It is better to offer sunnah prayers at home unless it is Sunnah to pray them in congregation in the mosque, such as th Eclipse prayer and nafl prayers before Jumu`ah.

1- If the recitation in tarawih prayer is kept short, then the number of rak`ahs is increased to 41 rak`ahs, as some of the imams said. 2- If a person wants to limit himself to eleven rak`ahs or thirteen rak`ahs in tarawih prayer, then he should lengthen the recitation and other essential parts of the prayer.