Yellow Jacket Ritchie 49137 3-1/8" Red Pressure, 0-800 psi, R-22/404A/410A Gauge Degrees F

would this gauge tell me how much puron is needed in my AC and heat unit?

Residue in gauges won't blend refrigerant even a little?

Does this fit the yellow jacket titan manifold

I have a r22 Mastercool manifold and hoses. Can just buy the yellow jacket high and low gauges and swap them out?