How about the cases of

(1) Linear Power Supply made use of linear region of linear voltage regulator?

(2) Switched Mode Power Supply made use of the on and off regions of linear voltage regulator?

(3) Efficiency of linear power supply = linear voltage regulator?

(3) Efficiency of switched mode power supply = linear voltage regulator or switching voltage regulator?

I felt confused about them! Please correct me! Thx!!!