Everybody here is kinda right, but there are other factors to consider, and the net result is that it’s usually not a case worth bringing.

The “Impossibility” defense says that in most cases, the “factual” impossibility of committing the crime is not a defense, but taking an action that is not a crime is a defense, and if raised must be proved by the prosecution. Even with “Factual,” the line gets muddy (the article cites a person whose appeal won after they were convicted of poaching after shooting a stuffed deer." Many jurisdictions have a “reasonable person” standard for that as well, where if the act is the sort of thing that might normally be expected to result in a crime (the most infamous case is two US military personnel who thought they were raping a passed out woman, but really she had died from a heart attack) then you get no benefit, but if no reasonable person would believe that their action would do anything, then it’s more likely to succeed. To answer one of your questions, being told the button sets off a bomb would be more problematic for our hypothetical asshole than being told it “just kills” somebody that would be a bigger problem than a Death Note notebook, but it’s not a simple yes/no.

So anyway, this then raises some questions. Was this button setup convincing? Who did the convincing? Why did they do so? Other defenses might arise out of these conditions: e.g. they were told that pushing the button would save a bunch of other people, trolley-problem style, or it was the police egging them on and telling them they needed to for XYZ good reason, and many of them will turn on the defendant’s thoughts, so in any jurisdiction where they are not obligated to testify (e.g. the United States), our very interesting defendant simply doesn’t, and their attorney argues that there’s reasonable doubt they thought the button would actually do anything.

Add on top of this prosecutorial discretion. A prosecutor knows all of this, and knows this is a loser of a case, so apart from truly bonkers hypothetical, they will not bring it.

TL;DR: By the letter of the law, very probably yes, but no one will ever get convicted for it.