Is it permissible to perform the Tarawih prayer as twenty rak'ahs, followed by the shaf' and witr as three rak'ahs, reciting a very short verse in each rak'ah? And is it permissible for the congregants to collectively repeat the supplication of blessings upon the Prophet and call out the names of the four Caliphs between every four rak'ahs?

The Prophet, peace and blessings be upon him, did not specify a particular number of rak'ahs for the Tarawih prayer, although his practice did not exceed thirteen rak'ahs. The matter is flexible, so one who prays twenty-three rak'ahs is not considered an innovator.

Shaykh al-Islam Ibn Taymiyyah said: "The night vigil prayer in Ramadan does not have a specific, fixed number of rak'ahs from the Prophet, peace and blessings be upon him. Rather, the Prophet used to pray thirteen rak'ahs and prolong them. When Umar gathered the people behind Ubayy ibn Ka'b, he led them in twenty rak'ahs, then prayed three rak'ahs of witr, with a light recitation. Some of the Salaf used to pray forty rak'ahs and pray three rak'ahs of witr, and some thirty-six rak'ahs and pray three rak'ahs of witr. All of that is permissible. The best option varies according to the condition of the worshipers. If they can tolerate prolonged prayer, then ten rak'ahs with three witr are better. Otherwise, twenty rak'ahs are better, which is what most Muslims do. If one prays forty or any other number, it is permissible."

Reciting one verse or part of a verse after Al-Fatihah is sufficient for the validity of the prayer, even if it is contrary to the Sunnah of prolonging the recitation.

As for the dhikr and separating the rak'ahs of Tarawih with the mentioned dhikr, it is not legislated; rather, it is an innovation. Abandoning it is a Sunnah. Ibn al-Hajj said: "It is necessary to avoid dhikr after every two tasleemat, and raising voices with it, and the muezzin's saying: 'Prayer, may Allah have mercy on you.' All of that is an innovation."