Hmmm. Okay, here's the thing. The list you just asked for is a big wide open internet full of information. Every single one of them could be a single question by itself, and probably would be unanswerable just due to its openness. It sounds, in fact, like some marketing person tossed some word salad at the public and hoped they wouldn't ask to see the steak.
There are literally hundreds of pages of information on the Splunk website about Security. There are entire applications written for Splunk to use to establish Security regarding your data center. It's best in class for that purpose.
Reusability and maintainability are a matter of best practices. Using apps written by other people, whether paid or unpaid, is a prime example of reusability. At the bottom line, however, reusability and maintainability amount to following best practices in developing your Splunk code and selecting apps. We can't tell you how to do your development, certainly not in a short post on answers.
Responsiveness, Elasticity and Resilience sound like somebody's buzz words. If you write a detailed description of what you mean by each of those terms, then we can point you to the documents that show you how they work in a splunk architecture. If you use best practices when you set up your system, and do your system sizing and your ingestion correctly, then the system will be responsive under very high loads. It will perform well under variable conditions, including occasional overload. And it will recover well from temporary or permanent loss of an indexer or search head. If that's what you mean by those terms, then that is covered, assuming you are following best practices.
However, we're not going to make any assumptions about marketing words like that. If you'd care to specify your exact metric -- and make sure whatever tools you are comparing Splunk to also provide their details in the exact same technical terms that YOU specify, not the happy fuzzy squishy words that come out of their marketing materials -- then we'd be happy to help you find out the correct answers about us that will help you make your decisions.