Info required about bahria town karachi construction by-laws

Assalam o Alaikum.

I need information about construction in bahria town karachi. While I know that its is mandatory to follow their by-laws about floor height, front, sides and back margins, front elevation etc … what I want to know is how much customization can you do in your floor planning? For example can you leave more space at the back than what is sitpulated in their by-laws? Do you have to keep sides and back elevations also as per their designs? What if I want to leave more space at the back of the plot to make a big lawn … will such customization be allow? Looking forward to expert advice.

Regards,

Ahsan.