In the future Selenium should be used as hobbes is deprecated.https://experienceleague.adobe.com/docs/experience-manager-65/developing/components/hobbes.html?lang=en

Check if the Java version is 11 and the supported Maven version is there.Also, run the maven command using the -X to see full debug logging.

Check https://experienceleague.adobe.com/docs/experience-manager-learn/sites/seo/sitemaps.html?lang=en for Sitemap.xml

You should configure the code structure outlined by Adobe for AEM as a Cloud pipeline. Another solution is to push code in your repo and use a build tool for packaging your code to Adobe's recommended code structure in the AEM cloud repo.

It is safe to delete any packages under/etc/packages and it will not uninstall any package.Packages under /etc/packages are just a backup for installing or uninstalling packages.The same is true for snapshots.

Error code 500 suggests something is breaking at the AEM end.Kindly, check AEM and dispatcher logs for errors.

you need to check errors in aem as cloud?

Can you provide the error details?

The only possible explanation for this behaviour is the text source editor does not support base64 encoding

You can go through https://experienceleague.adobe.com/docs/experience-manager-learn/getting-started-with-aem-headless/graphql/overview.html?lang=en for Graphql.