Reciting from different surahs in salaah

Q: In one musjid, the Imam Saheb read in the first rakaat of Fajr Salaah from the middle of Surah Tahreem,

يا أيها الذين آمنوا قوا أنفسكم و اهليكم

till the end of the Surah. Then in the second rakaat he read a different surah. Is there any reason for doing so? Would it not be better to start at the beginning of the Surah, read 2 pages, then in the second rakaat finish off the Surah?

Gambling

Q: What is the shari ruling on gambling. Is it actually mentioned in Surah Baqarah that it has some benefit for men?

Choosing a silsila for bay'at

Q: How is the Naqshbandi Owasia silsila for bay'at e tasawwuf? The current sheikh is Abdul Kadir Awan MZA who is the son of Hazrat Ameer Akram Awan ra.

This silsila claims that

- A Sheikh e kamil must able to take you in the court of Prophet (sallallahu alaihi wasallam) and make Ruhani bay'at with Prophet (sallallahu alaihi wasallam).

- This silsila is the only true silsila who is connected to darbar e nabawi (sallallahu alaihi wasallam).

- They claim to get benefit from a person in barzakh and the grave.

How is this silsila for bay'at? 

The thigh being part of the awrah

Q: Suppose a man came and sat in the masjid. He had torn pants above the thigh. Another man saw him and was trying to correct him, suddenly he got the thought that if he is sure that awrah uncovred will be invalidating prayer? He could not get any hadith or ayah that time in his mind. He became uncertain. So should he correct or not?