u can keep the upgrades u switch as long as they r the same tier..

like +2 with Y+1 and L+2 (gold tier)

if u switch from +2 to Y (gold to purple), then sadly u can only switch things in purple tier: +1 to Y to L+1

notice the color of the number:

Mys: +2, +1

Chase: +2, +1

As Yujin has explained, you can only swap between skills of the same level. If you swap to a skill of a lower level/rarity you will not be able to go back up and if you used fragments to obtain it then you will subsequently lose those frags.

This is outlined on the the Skill Trial Interface so in future please be aware and careful when changing skills.

I know but that wasnt the case... if i could go into system and print screen the items that i used, and the breaktrough that i did then i could provide a screenshot, but heck, you guys have close to 0 system/player info. I used vials to get some of the skills up to ther max grade, and for others i used hero shards, after about 15 mins i rechecked the skills and they were all down to ther original state. I mean i even got lucky and hit 2x maxed out skills with only 2 vials... so you can see my frustration. The main problem here is when i wrote to support they stated that i should provide a screenshot, how on earth would a person know that the game would bug out?! Explain that to me pls... altho i've stated in the previous post that getting a screenshot of the situation is rather impossible... tho i find it strange been playing a lot of client/web game, and they could all check the items that a person used, and at what time... and they got the compensation, if anything did bug out and *... i just got a typical copy paste respond... in short do you guys even care?!