が必要 => need; necessary N4
必要がある => Need/Need to N4
[必要「ひつよう」]はない => It is not necessary for A to be done N2
Needs, Requirements
必ずしも~とは限らない => Not necessarily; not always N3
[要「よう」]するに => A. In short/put simply, B N2
Adjectival, Descriptions
要するに => in short; in a word; to sum up; to put it simply ~ N2