What are the Core Teachings of Jehovah's Witnesses?
I've thought about this a lot and this is what I have come up with as their real core beliefs that cannot be changed:
1) They are God's one true religion
2) They are united (all believe the same thing, do the same thing, say the same thing -religiously speaking)
All other beliefs held by the JWs can, and do, change.
This is not a problem because changing beliefs about anything (like generation of 1914 etc) does not violate the two core beliefs.
Even when JWs believe different things (different levels of shunning for families, etc) they are all united in saying "it is a conscience matter!" No JW may openly have a different belief than the group on non-conscience matters.