Thank you

о какой-то преступности или преступнике

Не обязательно о себе?
"slang meaning to confess to a crime. ... An example of sing is for a person to admit they robbed a bank."

p.s. - о каком-то *преступлении*
преступность - общее понятие, явление

SING LIKE A BIRD means to divulge information with little coercion - usually about someone else, although the person may also be involved, but not necessarily.

“If we’re going to let Rick in on this heist, we’re going to need some collateral to threaten him with because he’s weak - the minute the police points a gun at him, he’ll sing (like a bird)”(= tell the police everything)

ОК, но в твоем примере Рик - (потенциальный) соучастник.
the minute the police points a gun at him, he’ll sing (like a bird) - ... он ПРИЗНАЕТСЯ во всем (расскажет о себе и о нас)

"рассказать всю подноготную (о каком-то преступлении или преступнике)", вообще говоря, может и случайный человек, и агент (mole).

Ok, here’s another example: “If we’re going to steal Ricky’s bike, we’ll have to wait until Mrs. Smith across the street goes to bed. She’s so nosy, she doesn’t miss a thing and already she can’t stand us, so she’ll sing (like a bird).”

Да, это другое. - "она нас обязательно заложит".

I think, I'll add both

👍🏼

should I delete mine?

I don't think so - it's good as an explanation.

👍🏼