A: DevOps is the combining of two historically disparate disciplines: software development and IT operations.
The primary goal of DevOps is to shorten the software development lifecycle and provide continuous integration and continuous delivery (CI/CD) with high software quality. You can use Power Apps build tools to automate common build and deployment tasks related to Power Apps if your DevOps platform is Azure DevOps.
D: Microsoft AppSource is now embedded in the Dynamics 365 home page and throughout the common navigation. It now includes a private gallery of apps available to you within your company. Select Get more apps from the home page or task pane, and navigate to the My Organization tab to see apps that are available to you.
Reference:
https://docs.microsoft.com/en-us/power-platform/alm/devops-build-tools
https://docs.microsoft.com/en-us/powerapps/user/app-source