where is possible to download Keynote 11.2 ?

If you have never installed Keynote from the Mac App Store, then you can only do so with the current version (12.2) if you are running Monterey or Ventura. The ability to obtain past compatible versions of Keynote for older operating systems from the Mac App Store is not available when you had never installed Keynote previously. Apple provides no user download site for past full versions of Keynote.

If you have a history of Keynote installations from the Mac App Store, and only if you are on Big Sur (macOS v11.*), you can get Keynote v12.1, but nothing earlier. If you are good with that version, then launch the Mac App Store on Big Sur, sign in with the same Apple ID you used to install it previously, and then press cmd+0 (zero).

You will now have a Purchased panel and Keynote should have a blue outline cloud with a down arrow. Click that. You may receive one or two dialogs, neither of which should you cancel. You are interested in the one that offers to install the last compatible version of Keynote for Big Sur.