Salam

I was wondering if anybody can answer the following:

1. Where do the 4 sisilahs originate from and how exactly do they lead back to the Prophet saaws? im talking about the sufi orders known as Qadriyah, Naqshbanidiyah etc

2. What is Ijaaza and how is it given? why is it nessessary? How can it be explained from the Qur'aan and the Sunnah? What are the prooves for it?

I should imagine these are simple questions to answer.