Both these adverbs are commonly used with perfect tenses [> 9.26.2], though in AmE they commonly occur with the past:
Have you seen 'Tosca' yet? - I've already seen it (BrE)
Did you see Tosca yet? - I already saw it (AmE) We use yet in questions when we want information:
Have you received your invitation yet? (i.e. I don't know.) We sometimes use already when we want confirmation:
Have you already received your invitation7 (i.e. Please confirm.)
7.29 Position and use of 'just'
Just (referring to time) has the same position as for adverbs of
indefinite frequency [> 7.40] and is used:
- with perfect tenses to mean 'during a very short period before now or before then' [> 9.26.2, 9.29.1]:
I've just finished reading the paper Would you like it7 I saw Mrs Mason yesterday She had just come out of hospital
Adverbs of time
- with the past, especially in AmE, to mean 'a very short time ago': I just saw Selina She was going to the theatre
- to refer to the immediate future, with progressive tenses or will: Wait I'm just coming I'II just put my coat on
Just has other meanings, e.g. 'that and nothing else': How do I work this9 - You just turn on that switch