can anyone do a detox if addicted to heavy drugs?

like heroin and cocaine? I was watching a documentary about a guy that was addicted to some painkillers, the name starts with V, he ate about 70 or 700 of these pills per day. then he did a detox in the hospital and I think he was cured, no more addiction. I want to help people, especially teenagers that are addicted to drugs and I’m wondering if they can also do the same. is it possible or is detox only for addiction to specific drugs?
I also wanna ask if detox is 100% succesful? can anyone be cured? does it costs a lot?
I read in a newspaper that a girl is selling her body for drugs and wants to get a new life without drugs, so I was thinking to help people like this.

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