Jem Aswad Senior Music EditorMarch 24 marks the 15th anniversary of the debut of “Hannah Montana” on Disney Channel, which was the show that introduced singer-songwriter and icon Miley Cyrus to the world. The letter was posted on Miley’s Instagram, and Hannah had a response that we’ll spare you the click for: “Nice to hear from you @MileyCyrus. It’s only been a decade.”Hi Hannah,It’s been a while.