Magento 2, You can create a Guest or anonymous customer empty quote programmatically using Magento\Quote\Api\GuestCartManagementInterface class.
You can create quote entry using interface GuestCartManagementInterface
How to add indexer dependencies in indexer.xml file?
You can manage the sortOrder of Indexer index id to call when indexer commands run. If you want to set custom sortOrder for an indexer id when indexer run you can set it using <dependencies> node with indexer id.
You can add below XML code to an indexer.xml file for set custom sortOrder of indexer while indexer commands run,
How to add CMS Static Block Programmatically using Setup Patchdata in Magento 2?
From Magento 2.3, Core modules use the declarative schema approach rather than setup upgrade scripts. This is the new recommended approach for Magento versions 2.3 and upper version.
All the InstallData and UpgrageData will be replaced by Data Patch Versioning.
Now you have to create Setup/Patch/Data folder and create the class file for create/update attribute or add sample data in Magento.