The sum bit is Goldbach's conjecture, which is open. The difference bit seems to be open as well (e.g. according to this source).
What if we allow the alternative? More precisely, has the following (seemingly) weaker question been resolved or is it open too?
Given $n\in\mathbb{N}$, do there always exist (not necessarily distinct) primes $p_1$, $p_2$ such that $2n\in\{p_1+p_2, p_1-p_2\}$?