Can I replace DWH by Splunk? I undestand it is impossible on 100%, but I want know border between DWH and Splunk. For example, I don't know how can we track slow chane dimensions and keep unique of any entity such as customer or etc.
Can we feed splunk by logs instead of usual data via Splunk Db?
There are some things you can do with Splunk that you can't do with a traditional data warehouse (that's what I assume you mean by DWH), and vice versa. There is an even larger area of things which are better done in one or the other. There is not really a border. There is a large overlapped area with tradeoffs between the two that gradually thins out as it becomes more difficult or less efficient to do in one or the other.
Yes, that's the normal and most common way to get data into Splunk.
Not sure what specifically you mean by Business Analytics. In the broadest term, yes, but you might have a more specific definition.