In the verb form, another word would be "obligated".
needs, compels, demands
Another word for not required is unnecessary.
Another word for obligatory is "required" or "necessary".
unrequired
required
required, obligatory
Another word for the adjective unnecessary is unneeded. Additional synonyms are superfluous, useless, worthless, dispensable, inessential, and not required.
whether it is required to send another PI?
A register
The likely word is "netted" (caught in a net, or slang for making a net revenue or profit.) Another similar word is "needed" (required, necessary).
Conscription is another word for the draft. Men were required to join the military/navy or RFC and serve.
There are several synonyms for the phrase "as needed." Some examples of these synonyms might be "required," "necessitated or necessity," and "desired."
level 9 is required to get another counter