Question

do we use of or off after dispensed. what is the difference?​

Answer 1

we use dispensed 'off'.

so, to explain the difference, let's take an example.

she is the principal OF the school.

the principal sent OFF the student who misbehaved.

so clearly, of refers to somthing its related to, and off is something you are getting rid of.

sorry for this long answer,

hence, dispensed off is correct as it got dispensed, i.e, getting rid.