well he lied, 2.10 is not compatible with 2.00 apparently
(1) Saves from 2.00 have been compatible with 2.05, as long as you followed directions, so no, he didn't "lie."
(2) Which version of 2.10 are you using? The older, buggy, virus-ridden one uploaded here by a disgruntled Patreon customer trying to sabotage the release, or the current Patreon build that we'll be getting tomorrow?
(3) There is a "safe zone" for saving games for export to a later version. That safe zone SAYS its a safe zone on the screen, but usually occurs around the "end of day" recap. It doesn't matter WHERE you are, it matters WHEN you are.