I've been facing this problem for two days that the infill changes that i make dont get applied. the printer prints at 100 rectilinear and only the first layer changes takes place. The solid infill is always rectilinear. i've restarted my system, downloaded new slic3r but of no use. what should i do ?

1) You should always save your settings after making a change and before slicing. Changed settings that have not been saved may not be applied.
2) IIRC the top & bottom solid infill patterns are only applied to the outer (top & bottom) single layers because they are purely for cosmetic purposes - all other top & bottom solid layers will be rectilinear.
3) If the top surface does not have a fairly large flat horizontal surface, the top infill pattern may not show up (e.g. on a dome, pyramid or sloping top).

Dave