1a] Should Taraweeh prayer be offered individually or in congregation? Is completing the Qur’aan in Ramadaan bid’ah?

1a]
became caliph, he united them behind one imam, Ubayy ibn Ka'b, who
united the people in one congregation on the orders of 'Umar ibn
al-Khattaab (may Allaah be pleased with him). 'Umar (may Allaah be
pleased with him) was one of the Rightly-Guided Caliphs, of whom the
Prophet (peace and blessings of Allaah be upon him) said: "I urge you
to adhere to my Sunnah and the way of the Rightly-Guided Caliphsafter
me; cling tightly to it." So what he did was Sunnah but he said, "What
a good innovation this is," because it was an innovation in the
linguistic sense, as they were doing something that they had not done
during the life of the Messenger of Allaah (peace and blessings of
Allaah be upon him), i.e., gathering to do this, but itis Sunnah in
the shar'i sense."
Majmoo' al-Fataawa, 22/234, 235
For more information, please see question no. 21740 and 45781
Secondly:
Completing the Qur'aan inRamadaan, whether during prayer or outside
prayer, is something that is praiseworthy. Jibreel (peace be upon him)
used to review the Qur'aan with the Prophet (peace and blessings of
Allaah be upon him) every Ramadaan, and in the Prophet's last year he
reviewed it with him twice.

And Allaah knows best.