Sterling was offside and interfering with the keeper and defender, Silva was well onside. The penalty was Sane diving over the Leicester defender's body.

Not the correct decision if it was for taking two touches. He slipped on taking it and the ball hit his other leg. It was unintentional so he therefore didn't "take" two touches. If you slip and eff up on the run-in you don't get a retake or anything, if he had an involuntary advantage it's the same. Those goals (not that it happens often) are never disallowed.