Does this work against your opponents synchros? Card text states “target 1 synchro monster on the field” but it doesnt clarify on yours. And also since it says material monsters should be on “your” graveyard, your oppenent cant special summon his materials back, right?
Yes, that's correct. If you use this on an opponent's Synchro, that opponent's Synchro will be returned to his/her Extra Deck, but no material will be summoned, since the materials won't be in your Graveyard.
So this card essentially gets rid of your opponent's Synchro without any cost or drawback.
That depends on a few things:
- Whether the fusion monster or the material has been banished before or not
- Whether the material can be special summoned or not
- Whether the fusion was summoned properly or not
Other than that, if the materials cannot be summoned, then yes, it would be a glitch.
Keep in mind that regardless of whose card you target with De-Synchro or De-Fusion, it checks YOUR Graveyard for the materials.
They also need to be able to Summon ALL of the materials used. So if you used a card that can't be revived, one left the Graveyard, you used one owned by the opponent, etc., you won't Summon anything.