1/ The Matador de Zorros is probably right. (1) is true (it's happened already), (2) is immaterial because Parliament voted to trigger Art. 50 and we've had 2 subsequent governments elected on a Brexit manifesto. The EURef is ancient history. The interesting one is (3), which may

2/ turn out to be true because May and the Tories were determined to make Brexit about leaving the Single Market and ending Freedom of Movement. Leaving the SM will be economically devastating, and ending FoM is what will rankle with the young (viz. future voters). Moreover, Mrs

3/ May and her party explicitly rejected any Brexit via EFTA (either like Norway in the EEA, or like Switzerland with its bilateral treaties, both with FoM). In those countries support for EU membership continues to fall, year on year. That is unlikely to be the case here.