Given the sentence:
These are the basic security features I need in order to operate safely.
And the sentence
These are the basic security features one needs in order to operate safely.
I am 99% sure that need should be plural in one needs. If so why would it be plural (we are using the word one)?
It would not make sense to say
These are the basic security features one need in order to operate safely.
I have heard it used in singular:
One need not worry.
Why does it work in singular there but not elsewhere?