Sayyed Muhammad Husaini Ragheb

A very good related answer is as follows:
http://www.sheikh-alsalami.org.au/2019/12/09/should-muslims-join-the-chr...

Sheikh Mufid (r.a) and Ibn Shahr Ashoub (r.a) have only recorded one son for Imam Reza(a.s) and he is Imam Muhammad al-Taqi al-Jawad (a.s) but some other historians have recorded five sons and a daughter for him.
As for Imam Jawad (a.s) the sons are Imam Ali al-Naqi al-Hadi(a.s) and Musa al-mubarqa' who is buried in Qom( Chehel Akhtaran) and he also had a daughter named Hakimah Khatoon who is buried in Samerra,Iraq.

The number is not mentioned, but in fact, if it's like a bunch of hair then prayer in these clothes should be avoided.
see:
Question: Does cat hair affect ones prayers?
Answer: If there is a few cat hairs (one to three) on a person's body or cloth, his prayer is in order but if there are more than that, his prayer becomes void, as an obligatory precaution.

https://www.sistani.org/english/qa/01130/

see also:
https://www.islamquest.net/en/archive/question/fa745

Salaam
According to Sayyid Sistani(may Allah lengthen his life) if one doesn't have a fixed job and a regular salary, he must take into account whatever he acquires for a year and if it doesn't get spent in his year's expenses, he should give one-fifth of it as Khums. So it's going to be a distinct "Khumsi Year" for each belonging, possession or finance you may get.

The Persian reference is :
https://www.sistani.org/persian/book/25103/4040/

Q no: 2301

According to Shia jurisprudence, Sajda should be performed on earth, and on those things which are not edible nor worn, and on things which grow from earth (e.g. wood and leaves of trees). The Holy Prophet (pbuh) also performed Sajda on soil and other things which are considered to be a part of earth such as sand, clay, stone, plants (wood) etc. not on carpet, rug, leather and plastic materials.  The Turbah of Imam Hussein (a.s.) on which Sajda is valid and which has superiority over other soils and things, is one of the manifestations of earth (or soil). Hence, Sajda is allowed on it.
www.islamquest.net

The wife will gain her dowry(Mahr) from the property because it's a debt + one 8th of the property because the dead person had children.
Then the rest of the property will be divided between the children with the formula of: "The share of boys is twice the share of girls"
وَإِن كَانُوا إِخْوَةً رِّجَالًا وَنِسَاءً فَلِلذَّكَرِ مِثْلُ حَظِّ الْأُنثَيَيْنِ
But if there be [several] brothers and sisters, then for the male shall be the like of the share of two females. (4:176)

Yes it's permissible if that girl was not married at the time of fornication.
But if may Allah forbid someone gets into sexual relationship with a married woman, they will become Haraam to each other for ever.

If there is no way to find the Qibla direction then praying to one direction is enough but according to Mustahab precaution if you have enough time you may pray 3 other prayers to the other 3 directions.
 

A woman in presence of non-mahram must cover all her body except face and hands(wrists down) -even feet- with loose clothes so that the body shape shall not be seen underneath the clothes.
So Abayah or Chador is not mandatory.

You are a traveler in this case and you can't fast.
But if you intend to stay in one place for at least 10 days then you have to offer your prayers completely and also fast.
Note that if you prayed a 4 unit prayer and you changed your mind (not to stay there for 10 days, then you have to pray completely and fast as many days as you will be there, like the next 2 days...)

A legal or Shar'ee swear will not take place unless it is in one of the names of God or one of His attributes.
It means that swearing to Quran or the name of Prophet or Imams will not end in a Shar'ee swear and if someone does something against that swear, they should not pay Kaffarah.
Of course we all know that saying lies even without swearing is Haraam and one must refrain from that.

Yes it is Mustahab(recommended) unless one is very weak, then it's better to do Iftar and pray afterwards