Correct. If he's the lying guard and something happened, or the truthful guard and nothing did, then in either case he would answer "no" to all the questions.

It's interesting, because it makes me think about the solution to the original puzzle. In that one, you don't care about the individuals' identities, you just care about the answer, so you actually don't know which one lies and which one tells the truth at the end. If the goal was to find out which one is which, you would need one more question: "and which one do you think I should take?" If he gives the same answer, he's the liar; if he gives the opposite answer, he's the truthful one. (Or just ask a question with a known answer first.)

Correct. If he's the lying guard and something happened, or the truthful guard and nothing did, then in either case he would answer "no" to all the questions.

It's interesting, because it makes me think about the solution to the original puzzle. In that one, you don't care about the individuals' identities, you just care about the answer, so you actually don't know which one lies and which one tells the truth at the end. If the goal was to find out which one is which, you would need one more question: "and which one do you think I should take?" If he gives the same answer, he's the liar; if he gives the opposite answer, he's the truthful one. (Or just ask a question with a known answer first.)

Maybe they get assigned roles each day at random to increase security?

If the goal was to find out which one is which, you would need one more question

"Would the other guard identify you as the liar if asked?"

The liar will deny it while the other guard will anticipate the liar's answer and say yes.

Ask either which way the other guard will tell you to take. They'll both tell you the wrong path.