"If I'm not mistaken" is a very common phrase. Use it when you are not 100% certain about a fact. You can also use it when you ARE 100% certain but you want to save someone's face. If I'm not mistaken, tomatoes are a fruit. If I'm not mistaken, the capital of the U.S. is Washington, not New York. However, the sentence "If I'm not mistaken for this information" is wrong. "For" is the wrong preposition here. You can say a person is mistaken ABOUT something. But more importantly, it doesn't sound natural to add "for/about this information." We almost alway simply say, "If I'm not mistaken,..." and then say the fact or detail, just like the examples above.

No, you can't say that. "If I'm not mistaken." Finish!

I've never heard that but I don't know if it's wrong. I usually use: If I'm not wrong or whether I'm not wrong. Are you Brazilian?