Not sure of the correlation between IT and the roll out of standards by the 3GPP, but the basic Standard for 5G is 5 years old, and both NSA and SA standards are now set. Having said that, 5G isn't just about extra speed (as you're in IT you should realise this) it's more about extra capacity, 5G is capable of far more capacity than the older technologies.
One of the easier reads of the standards
5G New Radio (5G NR) is a completely new air interface being developed for 5G. It is being developed from the ground up in order to support the wide variety of services
5g.co.uk
Your other questions aren't really relevant to the discussion, as they are about issues outside the standards discussed. But to satisfy your curiosity I bought my Mi 10 Lite from Amazon UK, it cost less than £200, (£183 iirc).
I don't buy phones because it gets a free screen protector or other accessory, that's false economy, I prefer to buy from a retailer that offers solid after sales support and buy my own screen protectors and cases.