I am using AEM 6.3 SP2 and I don't see any issues, what is the version you are using ?

Increasing sling.max.calls is not a problem, but you need to think about page performance if you author more than a certain number of items let us assume 1000 items in the multifield then it will directly impact on the page performance, sometimes it may take minutes  (20 to 30mins)  I feel it is not...

Check this, you will get the XML for all coral fields and it contains xml for multifieldhttp://keysandstrokes.info/aem-6-3-granite-ui-coral-3-components/

If the OOTB components are not supporting all of your requirements then you can use custom components, why people are creating custom components for basic functionalities is either he/she not aware of OOTB components or it is not easy to implement enhancements. because some times it requires additio...

Yes, there is no property to track user status under home/usersIf it is a new requirement then I suggest you to use Sling Filters, this will fire for every request, so you can read the username and write it in either separate log file or use impersonation and write a new property to the logged in US...

I think you cannot directly use content fragments or experience fragments in Mobile, but you can use CaaS, Generally, the mobile apps works on REST API's so you can build your front end either using Angular 6 or react Android or some other thing and using HttpRequest make a call to AEM content servi...

You need to contact Adobe sales team for this. If your company is already partnered with Adobe then you can request AEM trail version in SPP portal with your official email. They will provide the AEM trail version link with license key.Adobe Sales Team: https://www.adobe.com/in/products/request-cons...

Generally, you can call servlet different waysYou can call it using AJAX request, which normally you use to load the content without refreshing entire page$("button").click(function(){    $.ajax({url: "/bin/servlet", success: function(result){        $("#div1").html(result);    }});});You can also u...

Check this, it covers all possible wayshttp://www.aemcq5tutorials.com/tutorials/sling-servlet-in-aem/

Yes,  you need to declare new variables on top of it add AttributeDefinitions and you need to same variables name which were defined earlier