(a) When a street line, grade of centerline or curb of any street or sidewalk is established by the City Council or by a City officer duly designated for such purpose, such grade and alignment shall be official, and no person shall change such grade or alignment so fixed.
(b) The situation, range, heights, width and pitch of the curbstones and pavements shall be determined and established by the City Council or by a City officer duly designated for such purpose, and shall be complied with.