"AFAIK"is exactly correct. As far as you know.
Rest your heart and mind, its no longer an 8 track mag tape. Yes, many companies (not all) have pre loaded routes. Any number of circumstances on a regular basis changes routing. SIDs, STARs, traffic, restricted airspace, blah blah blah. Pretty much routine "stuff"
"Flying as UFO without squawking."
If you have been previously identified, you are not exactly an UFO. You just not squawking detailed information such as your altitude. When a flight crew realize they may have busted an altitude, investigation shows in many cases, they instinctively turn off the transponder. Not unusual.
Yes the hijackers of 9/11 turned off the transponder in 3 of the 4 aircraft. So now anytime a transponder is turned off, you are going to conclude it was a hijacking? Wow.
"ADS-B turned off"
Who really knows and more importantly who really cares. I can think at least a dozen or more times last year, pilots forgot to turn it on. Has no meaning in this specific moment
"Narita bound pilot got them on radio"
That report turned out to be false. Once again, more than half of what you read in the media is full of crap, half truths and lies
"Mobil phones online"
Most Asians here believe in ghosts. So if that floats your boat and make you want to believe that a land shark came up and bit them, have at it. Enjoy
Apparently they the plane's transponders were turned off intentionally but they weren't aware the airplane also sent at least engine data to Boeing and Rolls Royce that the plane was airborned for another four hours after it vanished from radar.
There are two online reputable news sites saying secret negotiation with the hijackers are ongoing, too.