F then 7 opens the F4HWN APPS menu and MENU runs the selected app, which is upstream's own wording in UVStudio's locales/en.js and what App/apps/app_menu.c does (KEY_MENU on an installed row calls APP_LaunchOverlay, which runs until the app exits; EXIT leaves). Verified in the emulator with Tetris.app installed through the page's endpoint: F,7 reads the app region eight times and shows the boxed menu; MENU reads once inside slot 0's code and the game's screen replaces the radio's; DOWN moves the piece and the game is still there two seconds later. The page's own hint now says so.
Worth recording: twenty keys short and long, the whole 79-entry settings menu and the multiboot menu all left the app region untouched -- the multiboot menu reads firmware slots, not apps. The entry point was written down in the flasher's translation file, not in the firmware source: when a feature's way in is missing, the host tool that installs it is the document.