Focusrite Control iOS has now been discontinued. See this article for more details.
Scarlett 4th Gen users: Focusrite Control 2 is available for iOS and Android.
Yes, you can use the Focusrite Control iOS app to control Red 4Pre/8Pre/8Line/16Line with RedNet Control 2.3 or later.
The app cannot be used to control other RedNet devices.
Please see the following articles for further information: