The extent of energy saved in the various situations described in the question will depend very much on the type pf appliance, the usage pattern of the appliance, and the practices adopted for energy saving. For example, let us take the case of switching of the engine of an automobile waiting at traffic signals and on other occasions when it is not moving. The switching off the automobile saves some energy while the automobile is stationery. But restarting the automobile requires more fuel than what is required for just idling of the engines while the automobile is not moving. Thus saving in energy will take place only when the halt at the traffic signal exceeds some minimum duration.
In cases of practice like turning heating down the reduction in temperature can be varied. The extent to which a lower temperature is accepted will have big influence on the amount of energy saved. In cases of practices like use of energy saving light bulbs, there is extra considerations of the extra energy used in manufacture of these kind of energy saving appliances. In case of some appliances the additional energy used or manufacture can be a significant as compared to the total energy saved during entire working life of the appliance.