Why don’t we see Medium range air to air missile with thrust vectoring? ?

Because there’s no need. If you are shooting a medium range missile chances are you’re not going to need to do a high off angle shot and by the time the thing gets to the target it’s motor has long since burnt out.

Most of the new medium range AAM have much less surface control area than the old missiles. For example aim-120 and aim-7. How is manuverability comparing the two??

I’d also be interested in how that effects their performance at high altitude.

Is tail conrol better than canard on missile?

Probably depends who you ask. The Python 5 uses canard but AIM-9X actually went FROM canards to tail control. ASRAAM, IRIS-T, U-Darter, all use tail control.