I want to be crystal clear and add much emphasis that something will happen if and only if a specific condition is met. I thought of If and only if and then and only then.
Can i use both in the same sentence to give emphasis to the condition that must be met?
"If and only if you are wearing your spacesuit, then and only then
can may you exit the spacecraft."
Would a native speaker express in such a way to give emphasis or that would sound unfamiliar in English?