Continuity mistake: When Ethan wakes up in the hospital he realises he's handcuffed to the bed. In the closeup of his right hand, the handcuff is around his wrist with its single metal bar facing out and the double bar facing Ethan, but when the nurse moves his gurney the handcuff is around his right wrist the opposite way, with the double bars facing out. Quite impossible for this to occur. (00:31:50)
Continuity mistake: When Ethan is hanging on the outside of the Burj trying to kick in the laser-etched circle of glass, his hand position changes from outside the circle to across the line of the circle as the shot changes from outside to inside the building.
Trivia: The number A113 (which appeared in Brad Bird's previous films The Incredibles and Ratatouille) makes two appearances here. The first is on the side of Hanaway's ring in the flashback sequence, and the second is verbally as Ethan's agent ID that he recites through the phone after he escapes from the hospital. (00:14:40)
Continuity mistake: This is at the fancy car park in India. Hendrick has just jumped off the platform. The briefcase as well as his body move in subsequent shots. Note the lines in the concrete floor.
Answer: He considers Hunt to be a friend, so did what he asked. In addition, by carrying out the deal he has ingratiated himself with Sidorov as well.