We have finished revising yet.
We have already finished revising.
Use already when something has happened before now, often sooner than expected: ‘We have already finished revising.’
Use yet in questions to ask if something has happened and in negative sentences to say it has not happened. It normally goes at the end: ‘Have you finished revising yet?’ ‘We haven’t finished revising yet.’
Check our grammar lesson on already, still and yet.
See ALREADY