What is the latest version of Opera that runs on OS X 10.5?
I have an old G4 Powerbook running OS X 10.5. What is the newest version of Opera that will work on it?
Because your Mac's hardware is based on the old PowerPC (and not the new/er Intel) architecture, the latest version of Opera that will run on your Mac is 10.63.
Choose either of those files that do not contain 'Intel' in their file name for the correct ones for your machine.