On Windows 10 Mobile Redstone Builds, Windows Insider app has been ditched in favor of in-built “Insider Preview Build” settings app. Until last Builds it was not possible to opt out of the Insider Preview programme using the settings. It was possible to pause Insider Builds for only a number of days. But now with Build 14385, you can use the settings to opt out of the Insider Preview programme completely.

Steps:

  1. You need to go to Settings–>Update & Security–>Windows Insider Programme and tap on Stop Insider Preview Builds.
  2. On next screen select “Need to stop getting Insider Builds completely”
  3. On next screen tap on confirm
  4. Restart Now and you are done.