Problem about the properties of convolution
Let h(t) be the impulse response of an LTI system.

1) x(t)*h(t)
   The convolution result gives the response of an LTI system with h(t) as impulse response to which the input is x(t)

2) x(-t)*h(t)
    The convolution result gives the response of an LTI system with h(t) as impulse response to which the input is x(-t). x(-t) is the reflection of x(t) by a mirror along jw axis

3) x(-t)*h(-t)
    The convolution result gives the response of an LTI system with h(-t) as impulse response to which the input is x(-t). The system with impulse response h(-t) has its poles and roots of h(t) exchanged between positive and negative half planes. So a stable system would become unstable and vise-verse (except for the poles and roots along jw axis).