I will be/stay forever with you.

[thehammer]

Which one is correct?

1- I will be/stay forever with you.

2- How long will you be/stay online?

3- I will be/stay there for one hour.

 

[5jj]

As usual with your questions, all are grammatically possible.

 

[Barque]

What's your context for each sentence?

You can make up a lot of grammatically correct sentences but don't you also want to make sure they make sense and fit a certain context?