From my own experience completing the form (but not yet having travelled) and that of my British brother and his Cretan wife who travelled last week, based on UK departure from Manchester to Heraklion:
- the middle initial/name. The form asks for a middle initial not name. Fill in the box (which will only accept one character) if you have a second given name; leave blank if not. *Possibly* (my own interpretation/guess) the airline will/could compare the PLF data with that in your passport to confirm that you are who who say you are, so if your passp[ort contains a second given name, enter the initial on the PLF application.
- one PLF can cover two people from the same family. My brother and his wife travelled on one PLF: we have completed one each, namimg each other as travel companions, to be on the safe side in case one phone fails or we lose one printed form. Note that if a family of three or more are travelling they'll definitely need more than one form.
- the form states 'family' not 'household'. In my opinion, there's no point in risking it by completing only one form for two people unrelated by birth or marriage.
- you receive a confirmatory email very quickly after submitting the PLF application. The QR code itself is indeed sent just after midnight on the day of expected arrival, so if you have an overnight flight you won't have the code when your flight lands (though I guess if airport wifi extends to the queue for passport control on arrivals it might come to your phone while you're waiting). In this situation shpwing the confirmatory email without the code should be sufficient.
As I said, this is how our family has interpreted the 'rules' and the family members who've already travelled have been allowed entry. Don't blame me if it doesn't work for you