Mathab

Asalaamu Alaykum Mufti.1. Why is following a Mathab compulsory?2.Is there reference in Quran pertaining to a must to follow a Mathab ?3. Isn’t all Mathaahib Sunnah of our beloved Prophet Moegammad S.A.W, so why Differentiate between it?4. If I am afollower of the Imam Shaafi Mathab R.A and i go on holy pilgrimage, why must i take wudu differently to perform Tawaaf? 5. is it permissible to break-off from Jamaa’ah to perform my Witr Salaah in the holy month of Ramadaan if i Follow a different school of tought? Shukran and Wasalaam.