Yes, you may pick Dragons from both your side of the field or your graveyard.
Yes, you can banish one from field and one from graveyard for example.
It is oddly worded if you think about it, but it does gain ATK for dragons in both the opponent's graveyard and their side of the field. I think the 'each' part is more important, the phrase could be worded as "For dragons that are on the opponent's field, or in the opponent's graveyard, this card gains 500ATK for each".
The pertaining card effect reads: "This card gains 500 ATK for each Dragon-Type monster on the field or in either player's Graveyard." It gains 500 ATK for each Dragon on the field, or in either player's graveyard. There are three dragons in this example, so it gains 1500 ATKfor each, a 4400 ATK total. Althoughthe card effect ismisleading because of the "or in either player's Graveyard,"you may interpret it as "and in both players' Graveyards."
Yes, both players need a monster in their graveyard for "Shallow Grave" to be used effectively. The card allows each player to return a monster from their graveyard to the field, so if one player has no monster in their graveyard, they cannot benefit from the effect. As a result, both players must have a monster available to utilize "Shallow Grave."
they are both dragons!
Their both komodo dragons.
If this mirror is reflective on both sides, then it can be both concave and convex. Otherwise, the two cannot act like one another.
They Are Both Lizards
Both of them are carnivores
combine them both so that there is a variety of dragons depending on what type of duel game you do either if its computer or card tip most reliable dragon card is destruction gandora every dragon in the graveyard results in 1000 xtra attack and defence points
They both have glass and they both magnify.
Komodo dragons eat goats, and any type of mammal it encounters, both live and dead.