Well I imagine that you can buy any seed all year around, only based on the greenhouses that we know are in game.
Nah, Harvest Moon games iirc had it so you could get the next season seeds on the last day of the season
Ehhh, then again they didn't have greenhouses to let players plant out of season crops, but guess we'll have to see how it goes down.
Well the Island games for DS had them, but they were kinda lame. And HMDS had a basement with sun stones, lol. But nothing much besides that.