Breathing in the drinking vessel:
I did not know anyone among scholars allowed breathing and forbade drinking in the same time. 
Using the left hand in using Miswak:
chapter on Miswak, Ibn Taymiyah (may Allah bestow mercy on his soul) was asked about Miswak whether it is better to use Miswak with the left hand, the right hand is or vice-versa? Should we rebuke the one who use Miswak with his left hand; and which is a better answer? He answered: Praise be to Allah, the Lord of the Worlds: It is better for a person to use Miswak with his left hand because Imam Ahmad reported this in the narration of Ibn Mansur Al Kawsag, and no one of scholars disagreed to that. 
The wisdom behind using Miswak:
Using Miswak was ordained for removing the remnants of the food from the mouth, and this wisdom is agreed upon among scholars.
Others said: Using Miswak is an act of worship. If this view considers Miswak a mere act of worship without considering its wisdom, it is not conceivable because all Muslims agree that the wisdom of Miswak is conceivable.
The ruling of circumcision:
Ibn Taymiyah was asked about a grown up and sane Muslim who fasts and offers Salah without being circumcised, is it permissible for him to do so? And what is the ruling of a person who abandons circumcision? He answered: If he does not fear the damage of circumcision, he has to do so because it is permissible and confirmed for all Muslims according to the consensus.
 Majmu` Al Fatawa: 32/209.
 Majmu` Al Fatawa: 108/21.
 Majmu` Al Fatawa: 109/21.
 Majmu` Al Fatawa: 110/21.
 Majmu` Al Fatawa: 114/21.
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