a few questions on this ckt. does the change in Vcc affect the bias condition of the transistor? if it did, how? does the amplifier continue to produce an output when Vcc is switched off? why?
when Vcc is change whether up or down but the base, emitter & collector resistors are not replaced, the bias condition will naturally change. change of temperature will also change the bias condition.
when you switch off supply, conduction completely stops unless you have a cap connected which will continue to discharge after the supply is cut off.