1. If you have an upgrade as a requirement you need to have that upgrade before you can use that spell in-game. If you set this to false it won`t check if there is any upgrade needed to use the spell/ability.
2. Example: to use the ability barrage you need the upgrade barrage. But if you set Check Dependencies to false you don`t need the upgrade to use it.
I'm on a page about incorrect corrections, and spent the better part of like two hours trying to get someone to understand that -5^2 = -25, not 25, and then that post had comments get reposted because that group is self sustaining, and that person was in turn trying to explain what I just explained to them. And I'm taking that as a victory