pixel_player98363620 I think you misunderstood Gamemaster's answer. Quests and maps are reset and start from the beginning so you will get all the items/rewards from the maps and quests.
Achievements and Treasures are never reset. Since you partially completed the event, the achievement levels you finished will still be done and the treasure parts that you collected before won't be collected a second time (but you will still get experience for clicking on the treasure. Importantly for Snow White, you didn't finish the achievement the first time so there are still 50 gems to collect for finishing it which offsets the 100 gems to buy the event. There are also 27 gems in the maps so if you finish it, you are only down 23 gems for buying the event.
If you restart an event that you fully completed, the achievement is already done so you don't get any of the achievement awards and you don't complete the treasure but you still get XP for getting to the treasure pieces.