Will Encore succeed if the move your opponent used before failed?

Question

Stressing the failed part here, not missed. For example, if you taunted your opponent from Stealth Rocks previously could you then lock them into it with Encore the following turn? For another example, if the opponent used Stealth Rocks but failed because they were already on the field, could they still be Encored next turn?

Thank you!

Answer 1

Yes, it will succeed.

It will make the opponent only able to use the move that failed.

Source

Answer 2

Yep.
Source: Whimsicott.