First two of them are not synonyms yet while they obviously should be, so I am requesting our moderators to merge them.
It’s not so easy with the other two. ‘accents’ is a synonym to ‘ударение’ now, and that seems quite confusing to me, because ‘ударение’ is not the only and, as far as I understand, even not the main sense for the English word ’accent’. Would not it be a synonym for ’акцент’ in sense of a pronunciation, typical to an area / social group? And should not it be ‘accent’ (in singular) rather that ‘accents’?