OP, strictly speaking I am sure contractually they can change the baggage allowance and/or their excess charging, I bet that’s in the small print. This is also an example of how companies change websites, mobile phone companies have done this repeatedly so yo cannot find the exact terms you signed up to.
That’s a different case as you pay monthly for a phone contract and if you don’t like the new T&C’s you can leave before they take effect, contracts have to have four parts, offer (what was on the website at the time), acceptance (“I accept the T&C’s”), consequences (would be in the T&C’s outlining what they’re liable for, and what you’re responsible for, paying on time, turning up sober with a passport, etc) and consideration (the payment). In the case of a plane ticket you should get what you paid for. Unless they had a clause that said they could change them unilaterally without notice (which they probably do have to allow for stuff like changes in the law about liquids in hand baggage), but then you’d have to argue that they were acting unfairly in their changes.
IANAL (or an airline check in desk clerk in Nepal).
p.s. Fancy a ride when you get back or will all those 4000m passes have killed your enthusiasm for the south east?