grads to trim.

Hi people.I really searched solutions of the questions which i will ask but cant find.forgive me if already exist.

Firstly i want to make grads (by lunch box) but only on the area which i already drew.Is it posibble to pick the area at the beggining?
and if its not; how can i trim waste area by grasshopper (there are many tools about trimming, sth wrong with me cuz i tried all and cant get it.)

the other question is about to angles and length.as i solved we can arrange number of grads but i want to do is arranging also angles between lines or dimensions.

i believe if someone help me it will be a big step about my grasshopper