1. First day of season.
2. That's because next season they'll be less competitive or their contract is ending.
For example, manager has reserve player, weak 4 stars (3* next season), contract ending. He wants to avoid expensive contract renewal and he wants to buy new 5-6* player.
3. No. Moreover, buy scout only in first day(s) of season or don't buy them at all. Wait until next season starts, then buy 3-4/8-9 U21 years old player.