Is the prayer of the person standing by himself behind the row considered invalid?

Recently, we have noticed the phenomenon of young boys with beautiful voices leading prayers in mosques. Is there a specific age for an Imam (One who leads people in prayer)?

I work as an Imam and since I have sustained a back injury, I lead the prayer while sitting on a chair and can`t make ruku or sujud. What is the ruling of Sharia on my prayer and that of those praying behind me?

What is the ruling of Sharia on holding more than one congregation concurrently for the same prayer in the same mosque?

Is it permissible to place a screen in the women`s prayer place displaying the Imaam as if he was in front of them so as for their prayer to be accurate; especially, silent prayer?

What is the ruling on joining the congregation at a place separated from the Imam`s? Is following the Imam, although he is two stores above, valid?

What is the ruling on reciting Al-Faatihah by the persons led by the Imam in non-Silent Prayer?

Is it permissible for the person offering Hajj or Umrah and staying at one of the hotels surrounding the Sacred Precincts to follow the Imam of the Sacred Precincts from his hotel`s Mosala (place of prayer), knowing that these hotels` speakers are connected with those of the Sacred Precincts. Therefore, he can listen to the call for prayers, the Iqamah and the prayer itself?

Does performing Friday Prayer at Home due to snowy weather suffice? or free one from the liability before Almighty Allah?

Is having religious activities by a group of deaf people, such as delivering lectures, religious competitions, and giving prizes, considered from the Qiyaam (voluntary night prayer) of the Night of Decree? Is a person rewarded for the Night of Decree if he perseveres on performing Qiyaam during the last ten days of Ramadan?

What`s the ruling on following the Imam from outside the Masjid when there is room inside to pray?

Is it permissible for the persons who volunteer, during Ramadan, to regulate the traffic and park the cars of Isha` and Taraweeh prayer performers to offer those prayers after the congregation leaves?

Is it permissible for a woman to lead women in prayer ?

What is the ruling of Sharia on allocating a place outside the Masjid for performing Taraweeh prayer?

If an Imaam stood to add a fifth Rak`ah and the Ma`moomeen (those praying behind the Imaam) were split into: 1- a group which is certain that he had performed four Rak`ahs, and remained sitting until they offered Tasleem with him.2- a group which is certain that he had performed four Rak`ahs, but followed him in performing a fifth Rak`ah.3- a group which is uncertain or arrived late and followed the Imaam. Which group is right?