If a person as a traveller stays in his relatives' home and if nocturnal emission (during sleep) occurs does it become obligatory for him to take bath before Salat al Fajr? Is there any condition which allows one the concession like an ill person who is not obliged to take bath. I watched Khutba of Hajj on TV. I saw Khatib leading congregational prayer of Zuhr and Asr simultaneously. Here my question is why did he pray 2 Raka'h of each prayer? IF I pray Zuhr and Asr simultaneously should I pray 2 Raka'h of each prayer (2 plus 2) or 4 Raka'h of each prayer (4 plus 4)? If imam performs Qasar prayer then what the native Muslims will do? Will they follow the imam or stand up after Salaam and complete 4 Raka'h?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

It is not permitted to resort to al-Tayammum (rubbing the face and hands with soil - performing ablutions with sand or earth) as a substitute for al-Ghusl (ceremonial washing) except in the following two cases:
1) If water is not available.
2) There is water but you cannot use it due to sickness or coldness.
As for giving up al-Ghusl just for shyness from people and performing prayer while you are in a state of major ritual impurity, this is not permissible and your prayer is invalid. In addition, such an action constitutes a major sin. Some Muslim scholars believe that a doer of this action is a disbeliever, since it is a form of mockery against Allah. So, dear brother! It is your duty to ask water from your relatives to have a bath before performing prayer. Shyness and weakness should not make you commit what Allah, The Great and Almighty, has forbidden.
As for combining al-Zuhr with al-'Asr and al-Maghrib with al-'Isha and shortening the 4 - Raka'h - prayer to 2, a traveller and Hajji at 'Arafah can do that. Other persons (residents) are not allowed to shorten their prayers although they can combine them in case of danger, rain and sickness.
If a resident performs his/her prayer behind a traveller, who shortens his prayer, the resident has to complete his/her prayer after the traveller ends his prayer.
On the other hand, if a traveller performs behind a resident, he/she has to perform his/her prayer as the resident without shortening it.
Allah knows best.