So we know that there is entropy, shadow, and other mana that represent the fallen god's spheres. This is a little confusing for me as we can see that those gods' spheres are now corrupted. However good gods' spheres, like spirit, can be used in their normal good form, or for evil such as Laroth is doing. So since it seems that good spheres can be used good and bad, is this the case with bad spheres? Can their be a mage that can master trust mana or foresight?
There are two ways to access a sphere, the divine path (through the influence of the gods and their agents) and the magic path (by the influence of man himself.
All spheres can be used for good or evil through the magic path. Through some of the evil ones tend to be corruptive (or put another way the evil gods tend to go after wizards that are dabbling in those arts, Agares tends to be the most powerful in this regard). So its possible to have a good mage who uses dimensional, body or entropy mana. Just like you can have an evil mage that used spirit, law or sun magic.
There is a difference between "can have" and "is likely". Evil mages tend to lean toward darker arts, good mages tend toward less corrupted spheres. Certainly at a high level many good leaders and empires despise and mistrust the corrupted spheres on principle (just like the Overcouncil can outlaw shadow, entropy and death mana).
So there could be a good mage that uses shadow magic, but he is playing a dangerous game and may get a little more attention than he wants, or may find the temptation the sphere offers to be overwhelming. Likewise an evil mage who channels a lot of sun magic will find himself drawn toward honesty, or one that channels a lot of law magic will find himself preoccupied with justice. Which may irritate both of them.
Don't overthink this and take my meaning to be that someone who uses sun magic cant lie and such. These are just tendancies. Slight influences built up over a lifetime, not hard laws.
The true versions of the corrupted spheres dont exist anymore. So there is no way to access the old versions of the corrupted spheres.