Which sentence would to grammatically correct?

Question

1) Remember never to do that ever again.
2) Remember to never do that ever again.
3) Remember to never to do that ever again.

Answer 1

1. is correct.

The other two sentences have split infinitives.

Answer 2

#1 is closest, but to have "never" and "ever" in the same sentence is redundant. I'd remove "ever."