Answer:
1) testable claims
2) What happens to us after we die? How did so much life appear on our planet when others seem devoid of any species at all? Who, if anyone, pulls the strings of our universe? Is it some all-powerful god in control or are there physical and mathematical principles driving the engine of our existence?
3)
Yes, classification system is still evolving together with our knowledge.
But, before changing the name (e.g. of a species) it is important to collect and gather a wealth of information in order to support that change. Classification system is still evolving. The reasons for the changes are DNA analyzes. It is the new way for discovering relation between organisms and put them in the right context (classification used to be based on morphological characteristics).
Change in classification can be shown in an example of fungi. In the 90s fungi classification included only phyla Chytridiomycota and Zygomycota. Now theyhave been classified mainly on the basis of characteristics of their sexual reproductive structures. So, there are 7 phyla now: Microsporidia, Chytridiomycota, Blastocladiomycota, Neocallimastigomycota, Glomeromycota, Ascomycota, and Basidiomycota