Question

No digues mentiras. Correct Incorrect

Answer 1

It's incorrect. The proper way would be: no digas mentiras. No dije mentiras.

Unless you're trying to say you didn't give lies, then it would be correct but one doesn't give lies, they tell them.

Di means I gave.

Answer 2

No digues mentiras. Correct Incorrect  

Answer : Incorrect.

Explanation : There is no verb tense in Spanish with the word "digues".

You could want to write the second singular person in the present in indicative mode of the verb "decir" = dices. "No dices mentiras" that means You do not tell lies.

You could want to write the second singular person in the present in subjunctive mode of the verb "decir" = digas. "No digas mentiras" that means I hope you do not tell lies.

You could want to write the second singular person in the present in imperative mode of the verb "decir" = digas. ¡No digas mentiras! that means I command you  do not tell lies.

$\textit{\textbf{Spymore}}$