Depends on how you are charging and discharging. If you ground one end of a capacitor and the other end ties to a resistor, with the other end of that resistor going to a switch that toggles between +V and ground, then yes there is a relationship. The time constant of the exponential equation will be the same. But if you use different impedances for charging than for discharging, then there will be different time constants and the relationship becomes only an abstract one based on the half part of the product that is determined by the capacitor value itself.
the time constant for both charge and discharge is time in seconds = capacitance in farads x resistance in ohms for the capacitors voltage to change by 66%
nope. discharge time depends on the circuit requirements, bit is pretty much immediate.
