Project Forecast/budget

Hi All ,

Project accounting in Ax 2012 R2.

I have a question regarding the forecast of project .

a) Is it mandatory to maintain the forecast ?
b) If i want to create the forecast for hour , Item ,Expense in one form ,what is common place to define the forecast for all types , instead defining in separate forms ( project details form - > Plan tab - Forecast for Hour , Item , Expense)
c) Without forecast shall i directly create the project budget ?
d) Can i know the pros/cons if do not define the forecast ( but defined project budget )

Thanks in advance