There have been lots of thread on this topic. All points have been addressed. In summary;
State/City - Use the information from your passport. Thailand "residents" cannot enter Thailand in this field (yet). Same advice.
Phone Number - The paper TM6 also asked for this. Nothing new, enter any number you like. The country code will default to that of your stated home country but that can be overwritten.
Departure - this is optional information. Do not enter anything in this section.
It seems they will accept the QR code on paper or on a "device". Note that it is not you that "uploads" the QR code, you simply display it for the immigration officer to read.
And finally, for the unwilling and/or incapable, it can be done on arrival. There will be a facility for this. But is it is likely to be busy it is probably best avoided.