Use maven plugin as explained in https://github.com/mickleroy/aem-sass-compilerI believe newer maven project archetype has in build support for react and angular which uses sass file so should have default plugin included in project. Please check

Check error.log what’s showing there. Meanwhile you can check for other urls like http://localhost:4502/crx/de.if it still shows 404 then your instance might be corrupted or you might have different have version.Check all those things and if it still doesn’t start then try stop and start the aem and...

When you look maven repo for those dependent jars at https://mvnrepository.com/artifact/org.jdom/jdom/2.0.2 you can look for the compile dependencies and check idle your aem or your Pom are using same version or different version

It forces you to do so because from dispatcher all nodes are not accessible to the end users as it will create a security issue. That’s why they have predefined the path where you can put your own custom code, js or css. If the reference fonts in outside of clientlibs the the problem might arise abs...

I assume it’s not for AAEMaaCS. After code deployment do you this service being registered at Felix console? 

That means your dispatcher is not configured correctly. You need to debug on the dispatcher by setting the dispatcher log as debug and check what happens with the request 

Check request.log and access.log of aem publisher

So when you request page from dispatcher does the request going to aem publisher and if not then you might need to check the dispatcher rules for shortened url

You can add css class based on condition and with respective cad you can hide and showdiv class="exampleclass ${true ? 'testclass' : ''}">

Multifield fields only appear when click on add and if drop-down is out of multi-field so i believe it won’t work for hide-show with granite:data but just check if that’s not happening so you can follow this https://www.linkedin.com/pulse/aem-hideshow-drop-down-select-options-more-than-one-values-vi...