Hadith regarding the Muslim Ummah

Q: Please enlighten me with the references of this hadith: Conjoined Hadiths from Musnad Ahmad: Jaabir (radhi-yallaahu 'anhu) narrated that Allaah's Messenger (sal-Allaahu`alayhe wa sallam) said: "Al Muslimoon Ummatun Wahida, Wa Biladahum Wahida, Wa Harbahum Wahida, Wa Salmahum Wahida". Is this a Hadith at all?

Hadith regarding perfect Imaan

Q:

  1. I read that no one will enter jannah unless they have perfect imaan. So if a person has Imaan but it is not perfect will he attain jannah? Quote hadith or quraan ayaats if possible.
  2. What is perfect imaan? If I commit a sin does it mean I do not have perfect imaan ?
  3. Can you send me the hadith which says how one can attain perfect imaan through salaam?

Hadith regarding securing a house in Jannah

Q: Is the following hadith authentic and in the proper wording ?

Umm Habibah bint Abu Sufyan reports that the Messenger of Allah (Sallaho Alaihe Wassallam) said: "Whoever prays twelve rak'at during the day and night will have a house built for him in paradise: four rak'at before zuhr and two after it, two rak'at after maghrib, two rak'at after 'isha, and two rak'at before fajr." (Tirmidhi, who graded it as Hasan sahih).

Can you send me any more hadith that says how to get a house in jannah?

Hadith regarding the prohibition of a man touching a non-mahram's hand

Q: Could you please provide the Hadith, with Rawi etc. concerning the strict prohibition of a man touching a woman's hand, since I had heard that "A man's shoulder touching that of a woman is worse than touching a swine . . ."

The Hadith is "It is better that a steel nail be impaled on one's head than that he touches the palm of a woman . . ."  (Au kama Qaala) or words to the effect.

My friend who works in a mixed workplace told me that women shoot out their hands for a handshake . . . once he dropped his keys and stooped to pick it up, and then arose to find the confounded hand still there. He avoided again by saying he's got to go to the loo.

[Later I advised that to say straightaway, "Being a Muslim I cannot touch your hand nor look at you." which might offend the greeter, but will please Allah.] Please guide. Allah has praised and described the Ulama, "Innamaa yakhshallaha min Ibaadihil Ulamaa." (Is this correct?)