Both yet and already are used with the present perfect tense.
Imagine that you and your friend are going to travel. There are many things to do, and you ask your friend if he has done these things:
In all the examples, use yet at the end of the question. Your friend might answer:
Use already in the positive answers, and yet in the negative answers.
There is one time you can use already in questions: it’s when something happens earlier than expected. If your son finishes his homework in just 15 minutes, you could ask: “Have you already finished your homework?!” because you were expecting it to take more time.