Hello!

There's nothing wrong about getting "Your skills did not change" for using vials since it is based on chance or the so-called RNG. Some players only take a few tries and get the skills they needed while some others try many times before they get the skills that they need. If by any chance you cannot get the skills maxed, then maybe you should collect his fragments and buy skill books manually since Asuma [Wind Blade]'s fragments can be easily obtained from various features of the game. And keep your vials and protects for other ninjas that are much harder to collect fragments.

Yes, it is possible. Believe it or not but my Kushina [Red Hot-Blooded Habanero], 10+ tries and got no skill change for me.