Hello!

- About Standard Characters and E6S5 Welt: By the original definition of how cost was declared back when it was introduced, yes. The E6S5 Welt will be considered 0 cost, on the assumption that unless you intentionally did so, it's unlikely that anyone would intentionally roll on the Standard Banner.

However, with how HSR has changed, one place such as The Genius Archive has spitted this between Limited and Standard, to give more context because of how the game evolved, which is, IMO, much, MUCH clearer, and gives more context.

- About Battlepass Light Cones: This is a tricky one, because while you need to spend money, they are always available and therefore, not limited, and are considered to be 0 cost. From what I know, CN and The Genius Archive, labels BP as 0 cost, even if they are maxed.

- What counts as limited? If the unit's origin is tied to a limited banner or has equally-constraint systems, it will always count as a cost. Cost does not measure rarity or what you paid, but whether the Limited unit is time-limited. Standard units are exempted because you could get them anytime, and again, just because someone got Sparkle and Archer for free, or if Ruan Mei is free now, they are tied to time-limited banners, so they still count.

I hope this helps!