@mommunism
@Silwith Right, it would be logical for the stasis to break if you reverted time to before it started, but only if you're working with real-world time, not time that's frozen according to the stasis, which would make it paradoxical. If you were working with time according to the stasis (which is one-dimensional), you cannot revert or advance it out of the stasis itself, that doesn't make any sense because the stasis encompasses the timeline. Hence he must be working with time according to the world, hence he has to send her back 25 years, not mere minutes.
No, i think you think the wrong way here, if his Grandpas Stasis is a Time-Stop it does nothing for the target aside from stopping the flow of time, it does not necessarily "forbid" or "prevent" the use of other Time-Magic on the Target. Think of it more as "Time-Stop" and the other One "Time-Revert", than the Time-Stop would logically "overwrite" by the Time-Revert, because it gives a conflicting Command to the Target. There is no indication for me that the Magic of his Grandfather disconnects the Target from the real world (like, how would you transport her then ect), it only seems to stop her personal time, nothing more. (You could still stab her or use other Magic on her or things like this, its only that, as long its not other time magic or something that completly annihilates the body, she stays in this "about to die"-status)
Sure, if it where an encompassed System you would be right, then it most likely wouldnt work (but even then it would be possible if Restoration is a more "powerful" Skill then Stagnation, something with a higher Rank that can just "break" the other Spell.)
And it is logical that Healing Spells dont work, because they are a "process", that uses Time, which isnt possible if time doesnt flow, but his Restoration only reverts that time from this point, is doesnt seem to need any process in/on the target before that.
So, your arguments are understandable, but there are possibilities where it works, especially since there is no "proof" for us that it works like in your theory ^^