The obligatory prayers must be offered while standing with the ability and freedom of choice, and it is not obligatory to offer them while standing with a justifiable excuse. Recommended prayers like the Witr prayer can be offered in sitting position, however it is recommended to offer it in two rak'as then.

Yes, it is permissible, but it was reported in texts narrated by the Ahlul-bait (peace be upon them) that it is not recommended.

There is nothing more required than being steady in the conventional and natural sense.

One must recite one full chapter after Al-Fatiha in obligatory prayers. Reciting one verse or a few verses is not sufficient. It is sufficient to do so in recommended prayers.

Based on an obligatory precaution, one should only recite one Surah after Surah al-Fatiha. But one can recite a further Surah if it is not intended to be a part of the prayers, but just as additional recitation of the Holy Quran.

The detailed rulings on the prayer is mentioned in the books of religious rulings and edicts. We can point out some differences to consider, like the following:
a) Reciting the ‘Bismillah…’ in the chapter of al-Fatiha.
b) Reciting one full chapter after the chapter of Fatiha, including ‘Bismillah…’
c) Prostrating on earth or what grows on it, provided that it is not consumed for food , or worn as clothing.
d) Wiping the feet in wudhu, instead of washing them.
e) Wiping the head and feed with the wetness of the wudhu from washing the arms.
f) In performing obligatory Ghusl, it is a condition to start with the head.

Yes, it is permissible, and there is no obligatory order.

It is sufficient in the bowing position to recite "Subhana Rabbiyal-Adheem wa bi-Hamdih", or "Subhanallah" three times. It is also sufficient to recite any sort of "dhikr" that consists of praising Allah, like "Alhamdulillah" thrice, reciting Takbir thrice or reciting "La Ilaha Illallah" thrice, provided that the said is equivalent to "Subhanallah" three times. The same applies to prostration except that "Subhana Rabbiyal-Aala wa bi-Hamdih" is to be recited instead of "Subhana Rabbiyal-Adheem wa bi-Hamdih". But, it is not sufficient to recite, "Subhana Rabbiyal-Aala wa bi-Hamdih" in bowing, nor is it sufficient to recite, "Subhana Rabbiyal-Adheem wa bi-Hamdih" in prostration.

Yes, it is recommended to offer the Salam on every one of them (peace be upon them) after the prayers.

The obligatory takbeer is only the takbeerat'ul-ihtam. The rest of the takbeers are recommended and not obligatory.

It is permissible and not disliked.

Yes, it is permissible, and it is permissible to do so in any language.

It is sufficient that the tip of the big toe is placed on the ground in prostration.

You should consider the two mentioned chapters as one during the recitation of the prayers. If one recites Surah al-Feel, he should recite Surah Quraysh after it, including the Bismillah.

If the woman did this while not being aware of its being wrong, then this does not affect the validity of her prayers. If she was aware that it is not legislated and insisted on doing this then the prayer is invalid.

Yes, it is obligatory on her to prostrate when hearing the verse of prostration. It is permissible without hijab, and based on an obligatory precaution it should be on natural earth like soil, stones, rocks and similar materials, or on what grows on earth provided that it is not consumed for food or worn as clothing.

If prostration cannot be done as stipulated, based on compulsory precaution one can bend as much as possible and place the forehead on what is permissible to prostrate upon.

It is obligatory on you to perform the prayer in a way that does not cause you harm and hardship, even if it is performed while sitting.

If he attentively listened to the verse of prostration during the prayer, he should move just his head down to signify prostration, and his prayer will not be invalidated. If he only heard the verse, then he should still do the same based on compulsory precaution. If he does not do so, he has committed a sin, but the prayer is not invalidated.

Yes, one should decide which chapter to read before reciting the Bismillah. However, the overall choice that originates from repeatedly reciting a particular chapter is sufficient. For instance, if he is used to reciting Surah al-Ikhlas (chapter 112), then it is sufficient if he read it without fully being aware of this decision.