Are there sentences grammatical?

1.If I hadn't broken up with my ex-girlfriend, I would have travelled to the UK with her in 2021. Such a shame.

2.Without your help, I couldn't have finished the task until tomorrow.

3.Without your help, I might not have finished the task until tomorrow.

Q1) Are all the sentences grammatical and natural?

Q2) I think they're all talking about the future event that cannot or couldn't or might not occur because of the past event. Am I right? I mean that they're NOT talking about the past event as below

4.Without your help, I couldn't have finished the task yesterday.

It seems like just because of the word "yesterday", the time the sentences refer to is changed to the past.