My question is, is it true? Is really possible that one with pilot license (foreing) can do this process and work for two years, under the F1 visa?
Yes and no.
It's not possible to get a 2-year OPT on a CFI course. An OPT period is only 1 year, unless pursuing a
full academic degree (Bachelor's, Masters, etc.) in STEM -- Science, Technology, Mathematics.
What they're probably talking about is a 11 month CPT (as part of the course) plus a 1-year OPT after graduation.
US regionals require at least 1,000 hours (with a suitable bachelor's degree). No US airline will hire you on an OPT to fly a CRJ "for a few months". There must be more to the story there.