I try to upgrade/downgrade MongoDB version using replica set (rs.add command)
I tried many test but I am not sure if below method are correct method

I try to find official Doc but I did not find

in situation

master member : 3.4 binary (with featureCompatibilityVersion 3.4)

test 1: rs.add (with 3.6 binary (with featureCompatibilityVersion 3.4)
test 2: rs.add (with 3.2 binary )

master member : 3.2 binary (with featureCompatibilityVersion 3.2)

test 1: rs.add (with 3.4 binary (with featureCompatibilityVersion 3.2)
test 2: rs.add (with 3.6 binary (with featureCompatibilityVersion 3.2)