Confusion about direction of friction

The direction of the dynamic friction for is always opposing the direction of motion. If it would not to that, the friction force would accelerate your object, which does not make sense.

You need to know that friction acts in a way to oppose relative motion of object

1st case

Since the log is moving up relative to incline friction acts downward working as an opposition

2nd case

Now there is only a component of mg which causes log to move downwards relative to incline so friction changes its direction by same logic.

The speed is decreasing because the force whi h caused it to move up is no more there and mg developed is in a direction opposite to velocity attained so retardation occurs and object eventually stops

If the log is moving after the cable breaks, the direction of static friction will be opposite to its velocity, so it will change direction.

But it is also possible that the log stays still after the cable breaks. In that case you will determine the direction of friction by saying that it should compensate the other forces. This direction will most certainly change in this case also. Note that the magnitude of this friction should remain below a certain value $mathbf{T} le mu mathbf{N}$, otherwise the log starts sliding.

There are other factors that could make the speed decrease, but it mostly depends on what you include in your model.