I'd appreciate it if you answered my question.
1,Is there a little difference between (1) and (2)?
2,Is there a little difference between (3) and (4)?
(1), I miss you.
(2), I've missed you.
(3), I missed you.
(4), I've missed you.
3, If so, which is correct?
(1) I haven't seen you for a long time. I miss you so much.
(2) I haven't seen you for a long time. I've missed you so much.
(3) I missed you since you left.
(4) I've missed you since you left.
I miss you- The person is not with you; you might be on the phone or writing when you use this. It could also be used to describe a pattern of missing the person- they go away regularly and you always miss them, in which case you could be telling the to their face.
I missed you- this just refers to the past. You could be talking abouty a long time ago, or when they have just arrived.
I've missed you- I'd use this when the person arrives.