Time Frame

we consider our time frame to be running with the shows, but there are of course going to he some deviations. For example, if a character is currently imprisoned (dead shot, deathstroke) we will just say they broke out if someone picks them up as a canon. Also, if a character dies in the show AFTER someone picks them up as a canon we say they survived.

So obviously then the ones that are already dead, like most of the metas seen in the flash cannot be used since, no meta has been seen that can ressurect dead ones

Pretty much. That rule is in place so if people pick up a character and it dies in the show they can still use um, but using already dead characters is a no-no.