We are not allowed to make any sort of promise. Even promises that we have every intention of keeping. No promises or coercion.
In my state both would get the interview thrown out. No doubt at all. I saw an interview thrown out when a suspect looked up at the ceiling and asked himself “Should I get a lawyer?” No one said anything. No one suggested he didn’t need a lawyer. The judge ruled that he should have been immediately re-Mirandized. No we are not allowed to even hint at talking someone out of invoking their rights. This guy was a murderer by the way.
We are allowed to lie about certain facts but certainly not about your rights. It’s also usually a bad idea to lie and I would only do it as a last resort.
Like I said above this is for my state. Each state has their own set of caselaw. Each state may have more strict requirements than federal caselaw or it may just follow the minimum requirement set out by the Supreme Court.