in IDE try Maven Reload Project / Generate Sources check your settings.xml also - adobe public repository

The use of Optional in Java is a way to deal with null values and avoid NullPointerException. It's a more modern approach and is generally considered more safer to avoid any runtime execution - the flow will continue to next line or function.   In general, it's recommended to use Optional when deali...

Didn't get your complete requirement. Author instance is where the authors/content writers - create content and manage content. once you upload the images to author instance - publish it to store the content in publish instance. Author - Publisher - has two separate instances to maintain content. As...

can you change ResponsiveGrid to container and try     import { ResponsiveGrid } from "@adobe/aem-react-editable-components";   to import { Container } from "@adobe/aem-react-editable-components";  Container component is the one that takes pagePath and itemPath props.

http://localhost:4502/security/users.html   1. is user expected to be created in my local? - yes 2. how user will get created in aem? - use http://localhost:4502/security/users.html - create user 3. how groups will be assigned like admin, author, reviewer, publisher and so on. - in user management y...

in error logs check for the build start details, if there is any information on restart.

do you have multiple sitemaps ?    The sitemap index is a way to link to multiple sitemaps. If you only have one sitemap, the sitemap index might not be generated because it's not needed. can you check error logs and see for any errors, if the above statement is not correct.

as @Imran__Khan mentioned below - issue is with either Permission issue or Resource Resolver not initiated properly - can you debug the issue or print log statements to see the issue?

Can you please check the Build Logs and Error Logs for more details.

local host may have corrupted or some other issue - please check the error logs for more details. is it happening with other instances also ? like DEV or QA or can you try with any other developer localhost or try with vanilla installation.