De evolve pokemon to it's initial form

[Ashketchum6149]

Hello everyone if anyone mod or higher staff reading this,  I have done so much hardwork to turn my snornut into glalie (now at lvl 46) ,i wanted to turn into froslass but I get to  know late that snornut directly evolve into froslass, i even managed to get female snornut  and a dawn stone, if there is a way to transform glalie back to snornut (lvl remain same obviously) 

Thanks