As long as it is clear that the contact stopped forward progress and resulted in the player going out of bounds, in 1 and 3 the clock continues to run. The clock stops for 2.
In 1 and 3 the runner's forward progress was stopped in bounds. If you spot the ball there, you're saying the play ended in bounds. In 2, you'd spot the ball at the out of bounds spot, the 26, since forward progress was not stopped in bounds, therefore the ball became dead when the runner went out of bounds.
If you take bama's "He wasn't wrapped up" approach, then you best be putting the ball at the 24 in scenario 1. If the runner clearly disengages and deliberately runs backwards out of bounds, then the "forward progress" spot is irrelevant. He went out of bounds at the 24, spot the ball there, clock on the snap.