IS there a way to reset these medals or do we have to change the names and hide the old ones.?
If by reset you mean remove every key that has earned it, you can already do this. Use world.GetMedal("medal name") for every single medal on your game to get a list of every key that has earned it, and then world.ClearMedal() for each key to remove it.

For scores just null every value for each key. It'll hide it on the scoreboard.
In response to Ruben7
hmm i see. But you wouldn want to null the players level :(
In response to Josblud
I meant null the scoreboard fields, with world.SetScores(), not the actual in-game vars o.o