Please I need your help in the NG pipe line design

NG Pressure : 7 bar

I have main line with 14″ diameter , 15 Km , my questions are :

1- I need block valve stations along the line or not , and haw I decide there position ? sine there are 7 small branches from this line

2- for corrosion protection system for the line , I need some guides haw I can design it

thanks all