Is it seven o’clock (yet)?

[sitifan]

1. Is it seven o’clock already? (The speaker didn’t expect it to be so late.)
2 Is it seven o’clock yet? (The speaker thinks that probably it’s almost seven o’clock.)
3. Is it seven o’clock?
https://dictionary.cambridge.org/grammar/british-grammar/already-still-or-yet
Is there any difference in meaning between #2 and #3?

 

[emsr2d2]

The difference is that #3 doesn't give any indication of whether the speaker is surprised or not. In context, it would probably be easier to tell what they mean. As a standalone question, it's just that - a simple question.

 

[Tarheel]

Is it seven o'clock yet?

It's probable that something is supposed to happen at seven o'clock, and the speaker is feeling impatient.