If you don't want the patch to increment if the build fails, you can always move the versioning part to the end of the YAML, where you put condition saying that if all previous other jobs/stages are successful then run the stage where you update the build number.

Once the build is successful, you can tag your builds with the successful build number. For Branching/Versioning, there is no one size fits all solution, you will have to work with your requirements and design the best solution for your team. This article is just meant to be a introductory/boilerplate on how to do versioning in Azure DevOps.