Added 4+5 to preview/stable process (#2545)

docs/Coding-Guidelines/GitCheckinToMainPolicy.md

@@ -8,8 +8,8 @@ code change is Experimental vs Preview or Stable.
 See [Final Decision: Release channels and cadences #637](https://github.com/microsoft/WindowsAppSDK/discussions/637)
 for the expectations of the various release channels.
 
-Note: If a contribution only modifies repo documentation and does not touch product code or assets an 
-administrator is welcome to bypass build & test policies on the pull request to bypass build requirements. 
+Note: If a contribution only modifies repo documentation and does not touch product code or assets an
+administrator is welcome to bypass build & test policies on the pull request to bypass build requirements.
 Other contribution policies such as code review requirements still apply.
 
 ## Policy: Preview and Stable (aka non-Experimental)
@@ -19,6 +19,8 @@ The following requirements must be met to checkin non-Experimental changes to ma
 1. API Review approval
 2. Tests
 3. Prepared to accept bug reports from the world
+4. Functionality is Feature Complete by a release's fork for Preview1
+4a. Approved Design Change Requests (DCR) can be made after Preview1. See the DCR process to approve these exceptions.
 
 Changes of a non-Experimental nature must meet these policies to be committed to the main branch.