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May I ask if all the following usage of modals are all correct? Thank you for taking your precious time helping me solve my doubt.

We will have finished it by the end of next week.

We ought to have finished it by the end of next week.

We can't have finished it by the end of next week.

We coudn't have finished it by the end of next week.

We could have finished it by the end of next week.

We may have finished it by the end of next week.

We might have finished it by the end of next week.

We should have finished it by the end of next week.

We would have finished it by the end of next week.
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You don't show any context, and they make no complete sense this way. Do some searches and see what the appropriate contexts could be.
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I would say all of them could be ok in the right context, apart from can't and couldn't. Also, I'm not sure about "ought to", because I never use it (I always use "should") and so I don't know when it sounds good (I don't even know how to pronounce it, LOL) Emotion: smile
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Comments  
BTW, re the can't example, this is more natural:
We can't finish it by the end of next week. Firm.

We couldn't finish it by the end of next week, even if we made some effort. Doubt/conditional. But could is rarely used for the future, some people could feel confused.
 Kooyeen's reply was promoted to an answer.
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