the base ID doesn't change with publishing - you can see it in the browser URL when editing channel details in dev.portal - it's a number of the 123456 kind. Have a look at ECP <rokuIP>:8060/query/apps (open in browser) for idea. For unpublished versions of channels, if they are added through a code, ID has some _ABCD suffix - when published, suffix is removed.
Also from what i remember you create channel as either private or public and cannot change that later, so will need to create another one for public submittal. Sidebar: if your mobile app is "primary" and Roku channel can't function without it, why publish the channel as "public"? It can stay private, with the app using ECP to check if installed on Roku player and link to screen to install it, if not