Q1. Can you construct the above quadrilateral MIST if we have 100° at M instead of 75°?
Yes, we can draw the quadrilateral MIST if we have 100° at M instead of 75°. (It will be a different quadrilateral!)
Moreover, the vertex T will now change. And since the sum of all interior angles of a quadrilateral is 360°, angle T will also change.