IF we work on collaborative project some of the machine is not updated and the codes or repository of your collegues are not build on the latest Flutter version thats why you need yo downgrade it.
To know what is your current flutter version you can type this command on any of your command promt.
flutter –version
to downgrade the flutter version at your current channel type this command.
flutter downgrade
Hope it helps to you on downgrading your flutter version on a specific channel using commands.