NO (this is for the second part of the question), not all blockchains apply the penalty or slashing in their protocols, since until now it is a mechanism that is used by blockchains that use a PoS, Proof of Stake , since they are the protocols that have the block validation mechanism.

I agree with the definition of slashing that you have explained and it seems that you have good understanding related to this topic as well as you have also a clear understanding that all blockchains don't use slashing because they have their own consensus protocols. I extremely agree with you that blockchains that works on proof of stake mechanism mostly use slashing mechanism.

I extremely agree with you the steps that you have shared with us that we can use as a blockchain user for avoiding any slashing mechanism as well as you have also make a clear difference between advantages and limitations of slashing so over all these are excellent efforts by you