I don't think there is any difference, either in choice of grammar or meaning, between, e.g.,
'Everything will be done by Tuesday.'
'Everything will have been done by Tuesday.'
except for the second one being more formal/grammatically rigorous. Is there?
Best Answer
This is a future simple tense, which means, 'everything' will be done in the future, with no indication whether you are doing it now(let's say it is sunday at the moment), at least it will be done by Tuesday.
Means, you are currently doing it now(from sunday to tuesday), clearly, this is future perfect tense. Will+have