Test / Review: Panasonic NCR18650B Protected 3400mAh (Green)

I got my order of LiitoKala protected NCR18650B from this seller:

https://www.aliexpress.com/store/product/5PCS-2015-New-Original-18650-3400mAh-battery-3-7V-Li-ion-Rechargebale-battery-PCB-Protected-For/217753_32585730747.html

Since these are my first and only protected 18650s, how do I know that they are indeed protected — they look like protected batteries, as per the description from this thread by HKJ: How to see if a battery is protected - they are much longer than ordinary 18650s.

How do I check that the protection will work (aside from shorting them, which I don’t want to try doing at the moment)?

I’d like to ask also what does “protection” really do? — does it protect from draining to too low voltage? from overcharging to too high voltage? from drawing too much current?

If draining to too low voltage, what might the the low voltage threshold — is it 2.50v? How about high voltage threshold — is it over 4.20v — will charging to 4.21v trigger the ‘protection’ or maybe over 4.25v?

I’ve tried draining the battery down to 2.50v momentarily (@ 1A drain rate), but I didn’t notice anything happen (no shutdown, after the load was removed, voltage recovered quickly).