There's no way a therapist could accurately predict any of these questions. That said, where I work, if a client asks if treatment will be successful, most people answer something like- "Hopefully therapy will help, but we really don't know. We can just do the best we can". I have never been told in my own treatment that I will be cured or that everything will be fine. If a therapist tells you that, it's a red flag as far as I'm concerned. There isn't much concrete evidence on the effectiveness of therapy, so Ts can only base it on experience. And that's subjective since once clients leave, a therapist has no idea what happens (unless they come back). The most honest thing a therapist can say is that they want to help you and will do their best. As for the pain, I think that's subjective, since therapy isn't necessarily painful for everyone, at least not in the context that I read about here. For a therapist to tell a client they know how they'll feel is presumptuous.

There are a lot of surgeries and treatments that promise to be successful and curative but aren't dor a lot of people. Granted success is still easier to measure, but there are an awful lot of people who've had back surgery who ultimately weren't cured the way they had hoped. Lots of treatments are a gamble and can even be risky. As consumers we need to be aware of that- and providers need to be more honest.