A question about the CE amplifier
A CE amplifier inverts the signal at the input; it doesn't phase shift it although, having said that, if the input signal were a sinewave, it would look like the CE amplifier produced a 180 degress phase shift.

Miller capacitance eventually turns a CE amplifier into a kind of integrator and this happens at the higher frequencies thus an inverter (180 degrees) becomes an integrator (90 degrees).