(a) The net flux is also tripled because as per Gauss law the net flux is proportional to the net charge enclosed.
(b) Regardless of the volume of the enclosed surface, if the net charge enclosed is the same, the net flux remains the same as per Gauss law.
(c) No change in the net flux as it doesn’t depend upon the shape of the closed surface.
(d) As long as the new location of the charge remains inside the Gaussian surface, there is no change in net flux.