If you don't want to listen to those four groups all agreeing that Catholic and Orthodox are the mainstream Christian church, and JWs and Mormons regard only themselves as real Christians, that's fine. But if you can't tell the difference between the Catholic-Orthodox history and the 19th-century origin of the JWs and Mormons who believe there was no church between the 1st century and themselves, that's a bit of studious ignorance. The tests I gave in my first answer suffice to demonstrate that the Catholic-Orthodox-Protestant unity has significant truth and the cults don't.

You haven't cited any Christian statement that contradicts me. You seem to be judging just on my offhand comment that God is a Law unto Himself as well as a Person.

But if none of us are true, how do you know anything? The argument still applies: the proposition "only testable propositions are knowable" is untestable, so if true it's unknowable and nothing can be known.

I linked you 50 propositions that can be tested and falsified, you haven't admitted seeing I did. Scroll back. When investigating all the major truth claims people make, including atheists, I realized that the core truths have always been accessed by humanity in a sufficient form, and so I found them in texts both ancient and modern. It's not necessary for me to defend the Bible as "inspired" when I merely ask that people start from a foundation of recognizing how truth claims are made.

TLDR: You still have no answer how you know truth: you've affirmed as your core a proposition that defeats itself. The scientific method would work better: affirm reality exists as the core, and that propositions merely reflect it, better or worse. Don't dismiss propositions you believe untestable, test those propositions that you can and more will arise. If you believe a body of laws exists, but it is beyond our current knowing them completely, that would be a much better core because it admits that reality is always greater than our model of it.