In the OVAs, he still hasn't been accepted into the high school, if I remember correctly. And for the comparison of TV ep 1 - OVA ep 1... I think the big thing you are referring to is the part about his underwear. However, in the OVA episode they are actually wearing his underwear, whereas in the TV episode Ako just comes across it while pulling out some clothes for him to wear after his shower. Sensing something is going on, Riko pre-empts her by taking his underwear from the bathroom. It's generally the same idea, but it happened in different ways, and thus could very well happen at different times.

It's entirely possible the OVA episodes are intertwined between the TV episodes as well. If you want to think of it like this... TV ep 1 they find his underwear... then instead of putting them back they keep them, so on the day of OVA ep 1, they are wearing them, making it a surprise again.

I don't know, I'm just trying to make logical sense of it. I personally don't really care for the actual order, cause either way, it's Wincest.