I don't know the answer to your first question as i am not an electrical engineer.

Your 2nd questions answer is :

When you stream movies for a lot of time on your phone in most cases the chances are that the processor has got warm due to lot of usage and needs time to cool ,the energy released is purely the heat losses that have been generated due to the movement of electrons from one point to another in the semiconductor (in this case the processor) on the basis of this you can say that, the energy dissipated is thermal energy just as in the case of a carnot engine where the efficiency of the engine (processor in the mobile in your case) is not 100%.

Another answer for this can be explained through pic given below and its understanding theory (if you understand it and are not a nerd stick to the first answer) :-

Waste Heat To Electricity

There are many known ways to convert a temperature difference into electrical energy. One approach is by using a thermoelectric device, where a change in temperature across a semiconductor material creates a voltage that causes electricity to flow, sometimes referred to as the Peltier-Seebeck effect. This device is still subject to the limits imposed by the second law of thermodynamics. In other words, this is a way to approach the Carnot engine limit, but not surpass it.