Thank you for the suggestion. However, if you read through my question you will see that I did all this without success.
And now I cannot even get into recovery mode, (by pressing vol. up and power), although I did this many times before the system update. Anyway, I don’t think I can use recovery mode for any solution to the problem.
Is there any possibility that the original problen <stuck in boot loop> could have been caused by a hardware malfunction? Maybe the phone got dropped or sat on.