Amazon S3 Data Store and Azure Data Store are the only supported implementations supported for external datastore for AEM for now. See (1) for more information.(1) : Configuring node stores and data stores in AEM 6

By default, if you don't run the version purge there isn't a  finite limit to the no. of versions of pages/assets  to be retained but that might affect  overall system performance Once you run the version purge, it then picks up from the config and by default it would 5 versions that are 30 days old...

You can follow a similar approach as in (1) to do this on project level.(1) : Experiencing Adobe Experience Manager - Day CQ: AEM 6.3.1.0 - Show Custom Banners in Card, List, Column Views of Touch U…

Can you see if you get any exception in error.log or browser console once you try to install a package?Also, I think it might be that your java temp directory is full so clearing that or switching the temp directory to a different location should help here.

Satya,There is no developer version  of AEM. You can download AEM using Adobe licensing site or can request a trial from (1)(1) : AEM Download Request Form

Please add the error.log after installing package along with output of belowOutput of http://HOST:PORT/system/console/bundles.jsonOutput of http://HOST:PORT/crx/packmgr/service.jsp?cmd=ls

Search for  com.adobe.granite.workflow.content in Package manager and reinstall this package and see if they are available now

Can you use CRXDE to manually navigate to /etc/workflow/models and see if these models even exists ?

Try a query like (1) and adjust the path which doesn't load. This might give you the nodes which are missing jcr:content nodes under 'test' folder(1) : /jcr:root/content/dam/test//element(*, dam:Asset)[not(jcr:content/@jcr:primaryType = 'dam:AssetContent' )]

How about classic ui? Can you see such folder/files in classic ui ?Can you switch touch ui views (column, card , list) and see if the folder/files appear? If they do, repeat the exercise and see if you get any exception in browser console or error.logUsually this happens when the node structure has ...