Yes, you are allowed to own or get cards listed on the Forbidden List. If you are following the Advanced Format, then you are not allowed to use those cards in a duel.
You can just change what type of forbidden list you want and than you can put in certain typeses of forbidden cards,but some will stay forbidden no matter what.
There is no way to put forbidden cards in a deck for a tournament. If the cards are forbidden then you can't use them its as simple as that. But keep an eye on the lists some cards may be taken off the forbidden list and you can then use them.
Yes. The Forbidden/Limited list does not restrict the use of cards mentioned for casual players. They are strictly for reference and the cards listed under "Forbidden" cannot be used (or are "forbidden") in official (Konami, Upperdeck Entertainment, Shonen Jump, etc.) sponsored tournaments or duels.
All forbidden cards were once very popular. They were either splashable (staple) cards or could easily form a One-Turn Kill strategy in a matter of a few turns.
there is no code it is absolutely forbidden to summon them
There's no cards that are used unless you mean in tournaments which is different which would be forbidden cards
You need to have 90.00% of all cards in the game to unlock a feature called banlist, with allows you to use 1 Forbidden card in your deck, but there is no way to use forbidden cards as normal ones.
If you have consent of your opponent.
No you can not
Well, god cards are actually forbidden no matter what. even if they look real they are all fake because they are so powerful and so many people want them they are forbidden cards and no longer allowed in the game.
There are no god cards actually in the game because if there was they would be in the forbidden list.
You might be referring to the Forbidden cards that have a small red circle with a slash going through located in the top-left corner of the card. Once you obtain 90% of the cards in the game, you will unlock the "Up to 1 Forb Card" Forbidden/ Limited Card List that will let you use one Forbidden card in your deck.