"De-Fusion" can only be used on Fusion-type Monsters. No exceptions.
De-Fusion can only target Fusion monsters. Ra is not a Fusion monster, so no, you cannot use it on Ra.
In any official Konami sponsored Duel or tournament, no. If it is a casual Duel, make sure that your opponent agrees on the effects and statistics of the card before you use it. Also, to maintain fairness if desired, use protective card slots so that you will not be able to discern the fake card from the real cards.
Magic Reflector is a Normal Spell Card and goes to the graveyard after the chain resolves, meaning it would not be much use if its protective effect ended right then.What Magic Reflector and Card Guard do is set up 'lingering effects' on the token they distribute, that are no longer dependent on the card that set it up. So Card Guard can leave the field, and the token will still work.
This would depend on the wording of the card's lore. If the card states that "...when this card is sent to the Graveyard..." or "...if this card is destroyed by a card effect...", then it would imply that the effects are activated when it hits the Graveyard. However, if the card states "...when this card is destroyed by battle...", then this would imply that the effect would only activate if it attacked or was attacked and destroyed during the Damage Step. As for Flip Effect Monsters, their effects would only apply if they were flipped face-up before they were destroyed. If not, then their effects are not activated.
no, not that I'm aware of, but you can use cards that negate effects like solemn judgment or dark bribe.
Defusion - 2012 was released on: USA: 22 November 2012 (video premiere)
The cast of Defusion - 2012 includes: Aeneas Middleton as Mr. Steinberg - Police Officer
De-Fusion can only target Fusion monsters. Ra is not a Fusion monster, so no, you cannot use it on Ra.
The cast of Defusion 2 - 2013 includes: Aeneas Middleton as Mr. Steinberg - Police Officer
To let things through the cell membrane
Defusion 4 Bio-Cell System - 2014 was released on: USA: 31 October 2014 (video premiere)
If it is a corporate card I would imagine it is in the name of the company and not your name. If that is the case it shouldn't impact your credit.
Yes, because it is a quickplay and can be activated during the battle phase.
Defusion 3 Skynum - 2013 was released on: Japan: 24 September 2013 (Tokyo) UK: 24 September 2013 (London) USA: 24 September 2013 (video premiere)
Yes, it is a good card; negating monster effects is always welcome.
I think you mean diffusion - the movement of liquid or gas from one area to another?
Dark World Monsters have to be discarded 'by an effect' of a card. If you discard it as a cost, like that for Lightning Vortex, this will not trigger the Dark World card, and you will not get its effect.