They are twenty-one in total
Amongst them that which relate/apply to all worshippers in all prayers, and they are seven in total.
And amongst them that which are specific to some worshippers in some prayers, and they are fourteen in total.
As for the general:
1- The wording of takbir for the tahrimah
2- The first sitting
3- The tashahhud in the two sittings
4- Stillness in bowing and prostrating
5- Performance of every obligatory act (fard) in its place
6- Performance of every compulsory act (wajib) in its place
7- Exiting with the wording of salam
As for the specific:
1- Specifying the first two units for recitation
2- Fatihah for the first two units
3- Limiting the recitation of the fatihah to once
4- Adding a chapter, or three short verses or one long verse to the fatihah
5- Preceding the surah with the fatihah
All of these are for the one who must recite
 This is the position favoured by the author of al-Wiqayah (p.145) and was declared to be the correct position in al-Hidayah (1/46). Al-Tumurtashi said in Minh al-Ghaffar Sharh Tanwir al-Absar: ‘A group chose the view the tashahhud in the first sitting to be sunnah, however the Zahir al-Riwayah is that it is compulsory (wajib), which is the more correct position’.
 It is that the body parts when bowing and prostrating are still for the length of a tasbihah, this is likewise the case for being still between the bowing and prostrating, and the two prostrations. Fath Bab al-Inayah (1/234), Sharh al-Wiqayah (p.146)
 It is to perform every act in its place and order in the prayer without delay. Al-Jawhar.
It is possible that this compulsory act (wajib) also encompasses the keeping of order of those actions that occur a number of times in one unit such as the prostration (sujud), or in the whole prayer such as the number of units because they are compulsory (wajib). Fath al-Qadir (1/241), al-Bahr (1/315), Dur al-Mukhtar (1/309-310), Minhah al-Khaliq (1/314-315), Rad al-Muhtar (1/310), Sharh al-Wiqayah (p.145)
 Meaning in its place that it is legislated for it to be performed without any delay. Such that if the one praying finished reciting the fatihah and pauses silently for the length of a rukn the prostration of forgetfulness is compulsory upon him. Al-Jawhar
 Meaning twice, once to the right and once to the left without the wording “alaikum” being compulsory. However it is recommended to say so. The congregations following of the Imam ends with first salam before the saying of the word “alaikum”. Al-Maraqi (p.253), al-Tanwir and Dur al-Mukhtar (1/314)
 Al-Nablusi said in al-Jawhar: Meaning in the obligatory (fard) and compulsory (wajib) once without repetition. Such that if it is repeated forgetfully the prostration of forgetfulness (sujud al-sahw) is obligatory upon him. It will be mentioned later in the chapter of permissible acts the permissibility of repeating the fatihah in the optional prayers.
The basis of this is that is: ‘it is reported from Muhammad bin Hasan al-Shaybani (Allah be pleased with him) that he said: the one who recites al-Hamd twice in the first two units must perform the prostration of forgetfulness. Because he has delayed the recitation of the chapter by repeating the fatihah. If however he recites al-Hamd then a chapter then al-Hamd he does not perform the prostration for forgetfulness, as it is as if he recited a long chapter’. As mentioned in al-Badai (1/167).
However in Hashiyah al-Shalabi ala al-Tabyin (1/128) it is mentioned that: ‘the repetition of the fatihah in one standing is not legislated. The author of al-Dirayah said: but it is mentioned in Fatawa al-Itabi that the repetition of the fatihah in the optional prayer is not disliked due to a narration regarding its like. Ibn Amir Hajj said: Allah knows best about the authenticity of this’.
Likewise in Majma al-Anhur (1/148) it is mentioned: ‘If a compulsory act (wajib) is repeated it is not necessary to perform the prostration of forgetfulness. However in al-Khazanah and other works it says: The repetition of the fatihah in the first two units makes the prostration of forgetfulness necessary. It is possible that it be said: that the repetition does not make it necessary, rather the leaving of the surah does, because it is necessary that it follows the fatihah. It should be stipulated as being specific to the obligatory prayers, because the repetition of the fatihah in the optional prayers is not disliked as mentioned in al-Quhistani’.
It is mentioned in Rad al-Muhtar (1/460-461): ‘If the fatihah is recited twice in one of the first two units the prostration of forgetfulness is compulsory, due to the delaying of a compulsory act (wajib) which is a chapter as mentioned al-Dhakhirah and other works. Likewise if most of the fatihah is recited then repeated as mentioned in al-Zahiriyyah. As for if the it is recited before the surah once and after it once it is not necessary as mentioned in al-Khaniyyah, and this was chosen by the authors of al-Muhit, al-Zahiriyyah, al-Khulasah and was declared to be Sahih by al-Zahidi as it does not necessitate delay. Because bowing is not compulsory at the end of a surah, for if he joins between a number of surahs after the fatihah nothing is necessary upon him (in terms of sujud al-sahw) as mentioned in al-Bahr
. The author of Sharh al-Muniyah said: it is stipulated with the first two units because limiting to once in the last two is not compulsory, such that sujud al-sahw is not necessary by the accidental repeating of the fatihah, even if it is deliberate it is not disliked as long as long as it does not lead to the lengthening of the prayer for the congregation or the unit being longer than the one before it’.
 Meaning with the fatihah in the first two units of the obligatory (fard), and in all the units of the optional and witr prayers. It is sufficient to recite the shortest surah such as al-Kawthar or that which is similar in terms of length which is three short verses. It is likewise sufficient to recite one or two verses which are equal in length to three short verses. Tanwir al-Absar (1/308), Nur al-Idah (p.248), Dur al-Mukhtar (1/308)
 Due to the Prophet (Allah bless him and give him peace) regularly performing it. So if the person praying accidentally recites a surah first, then realises and recites the fatihah, and then goes onto recite the surah, he performs sujud al-sahw. Tanwir and Dur al-Mukhtar (1/308), al-Maraqi (p.249)
 Meaning these five compulsory (wajib) acts are compulsory upon all those who must recite, they are: the Imam, the one praying alone, the one who joined the prayer late and missed some of the units. Alternatively the above five compulsory acts are not obligatory for the one praying behind the Imam, the illiterate and the mute. Al-Jawhar