When power is fed to port 1 what is the power at the other ports?
port 1 and port 2 are collinear arms
port 3 e plane
port 4 hplane
I would guess you would get mostly power out of 2 and 3 and a little less out of 4. That is not how they are designed to be used though. They are for correlated inputs simultaneously at 1 and 2, or input at 3 or 4 alone.
could u explain it's(magic tee) use as a duplexer?
This website is a great resource for a lot of fundamental RF circuit threory:
Microwaves101.com - Couplers
But I think this may shed some light on your question, especially the part right after the first picture.
RatRace couplers
and this:
Waveguide magic tees
If the two loads are identical (can be identical reactive), and 4th port is terminated with proper load then input port will have low S11 regardless of two identical load impedances. Any reflected power resultant standing wave voltage at input port from the two loads will add at terminated point and cancel at input ports yielding the low input VSWR.
You can analyse the magic tee by looking at it as quarter wavelength matching stubs.
When the two loads are amplifiers, they can change their impedance with input drive power or temperature but must track together so their input impedance is the same for the magic tee to work.