How to use the word "never" correctly?
i promised never to do it.
i promised i would never do it.

i know the second one is definitely correctly but what bout the first one?
can we put "to" after never?

Question

How to use  the word "never" correctly?
i promised never to do it.
i promised i would never do it.

i know the second one is definitely correctly but what bout the first one?
can we put "to" after never?

Answer

I think they are both correct without "again" at the end.  If you add again to the end it implies that you have already done it at least once.

Answer

The first sentence is correct.
The second sentence would be better as:
"I promised that I would never do it again."
Intentions have two form：to-infinitive or that-clause
The first sentence is the to-infinitive form
The second should be the that-claus form

Answer

Both sentences are correct but feel incomplete... You can add "again" at the end.

I promised never to do it again.
I promised I would never do it again.