Go through this release note first. make sure you followed all the necessary steps and made changes accordingly. We did the same last month. https://experienceleague.adobe.com/en/docs/experience-manager-65/content/release-notes/service-pack/6-5-21

You need to add another property cq:showOnCreate="{Boolean}true" like this   <redirectType jcr:primaryType="nt:unstructured" cq:showOnCreate="{Boolean}true" sling:resourceType="granite/ui/components/coral/foundation/form/select" fieldLabel="Redirect Type" name="./redirectType"> <i...

Please try this query.   SELECT * FROM [nt:base] WHERE ISDESCENDANTNODE([/conf/global/settings/dam/adminui-extension/metadataschema]) AND [jcr:primaryType] = 'nt:unstructured' AND [sling:resourceType] = 'dam/gui/components/admin/schemafield'

When you make change on component it will update all of the places on content where you have used it. But existing data might be lost based on your implementation.   check the documentation here https://developer.adobe.com/experience-manager/reference-materials/6-5/granite-ui/api/jcr_root/libs/grani...

Hi,   path=/content/dam/{path} fulltext = Technical details page p.limit=-1 type=dam:Asset   this should return all resources type of dam:Asset under the path specified. Can check examples here. https://github.com/paulrohrbeck/aem-links/blob/master/querybuilder_cheatsheet.md  

There is a acs-commons tool for managing oak index. Can check that also. https://adobe-consulting-services.github.io/acs-aem-commons/features/ensure-oak-index/index.html

If the request is passing through cdn and dispatcher, can check if cookie header is allowed

on spa there is not need of data sly use. Because front end is not Sightly there. On SPA you send all the props to react/angular side. And based on the props show hide logics are on angular/react.Generally on spa we expose all the props to react or call a servlet for backend data

yes, those extra properties are there because we are using acs commons ensure oak index.

yes same for author and publisher.and we don't change content fragments programmatically. Only the author changes the content fragments.