Participants in congregational prayer (Salat Al-Jama’ah) don’t need to recite Athaan nor Iqama has far it has been recited by Muazzin or others.
No. There is no single narration that the Prophet ever led Taraweeh neither in Sunni nor in Shia books. Taraweeh was initiated in the year 14 after Hijra by Umar Ibn Al-Khattab as he himself called it a Bid'ah and said it is a good Bid'ah. (Saheeh Al-Bukhari, Salat Al-Taraweeh.)
Yes it is better to pray with congregation than praying alone even if the congregation is with Sunni Muslims. When you pray in congregation with Non-Shia Muslims, you need to recite Al-Hamd and other Sura yourself but with out clear voice.
Eid Prayer is allowed to be prayed in congregation because it is in its original form an obligatory prayer in the presence of the Prophet (SAWA) and the Imam (AS). It is not like Salat Al-Lay or Nafila or Ghofaila etc which is always recommended. The reason behind praying Eid Namaz in congregation is its original form which is Wajib.
It is a term in jurisprudence within the conditions of the person who can lead a congregational Prayer to Aadil عادل. Aadil means a pious person who does not deliberately commit sinful acts, and if it happens that he committed a sinful act, he immediately repents and seeks forgiveness and never insists on wrong. Such pious, God fearing, obedient person is called Aadil.
(Just) is a literal linguistic translation of Aadil but it does not include the full meaning of the term Aadil.
Congregation Prayer (Salat Al-Jama'ah) becomes invalid if the person deliberately does Rokoo' or Sojood or any other act of Salah before the Imam of Jamaa'ah. Reciting Tasbeehat or Tashahhud or Salaam before the Imam of Jamaa'ah is Makrouh but it does not invalidate the Jamaa'ah while doing the acts of Salah before the Imam of Jamaa'ah does invalidate the Jamaa'ah but not the Salah. Salah then becomes Furada (individual) when the Jamaa'ah is invalid.
Joining a congregation prayer is allowed in every Rak'ah till before the Imam of Jama'ah raises his head from Rokoo'. If you join during Qiyaam (Standing) or Rokoo', it will be counted for you as a Rak'ah.
We are not allowed to join congregation prayer after Rokoo' except in the last Rak'ah just to get the reward of the congregation prayer but it will not be counted as a Rak'ah.
If you are in hurry and can't wait till Jama'at starts, you can pray individually (Furada) but it should not send a wrong message of disrespect to the Imam of Jama'at or to the participants who are waiting to join the congregational Prayer.
It is not allowed during obligatory Prayer (Salah) to add Rokoo' or Sojood because it will invalidate the Salah. Reciting any of the four verses of obligatory Sajda is not allowed in obligatory Salah. If you do Sajda for reciting or listening to any of the four verses of obligatory Sajda, you Salah becomes invalid and you need to perform the Salah again.
Thank you for your question. One of the conditions for a prayer leader according to the School of Ahl al-Bayt (as) is that they are baligh. If they are not baligh, that prayer cannot be lead by them and so if someone participated in that prayer they will need to repeat it.
May you always be successful
congregational prayers are much more better than praying alone. The reward of praying in congregation is many folds more which can be hundreds or thousands of times.
Congregational prayer has conditions including the conditions of the Imam of Jama'at. Woman can lead women only in prayers and she should stand in the first row with other women and not to stand ahead of them.
The main requirements for the Imam of Jama'ah are:
1. He be well versed in the rulings of fiqh and prayer in particular.
2. A man of piety and righteousness, with inner taqwa, high moral standards, and 'adalah, which means he does not commit regular sin.
3. His pronunciation and recitation is accurate.
4. Other things mentioned in the fiqh books.
If there are numerous people who broadly have these main requirements, then the person who is more learnt, or with more taqwa, or better recitation, is presented as the Imam Jama'ah.
And Allah knows best.