growing hair

If the hair was shaved(or otherwise removed), does it mean that all this hair will be anagen when it starts to grow out?
How long is anagen stage for different parts of the body?
How does the follicle ‘know’ that the hair was shaved to restart the growth process?

Hairs that return after epilation or continue growing after depilation are actively growing and easier to kill.

You can read about growth stages here;

Regrowth charts

Shaving a hair has no affect on growth cycles. The hair just keeps moving through its cycle. Epilating a hair may cause a hair to start growing sooner or later than it would have if it were not removed, but removing hair above the surface has no effect on its growth.