Okay so. Boobs out. Questionable? I've see this some places. Is it required to have the genitals out for explicit? Or do the nipples also count?

This may be helpful: https://e621.net/help/ratings

Nurps aren't inherently explicit, any genitalia or butthole is- no matter how stylized or small.

It's female nipples that make a post Questionable, not the overall breasts themselves. Featureless breasts can qualify as Safe.

For a post to qualify as Explicit, it would need to have the genitals be visible, including high detailed ones through clothing, as well as sex (even if no genitals are seen), anuses, and gore.

Have a gander at the site ratings wiki to see a breakdown on what's required for each rating.

boobs out with nips and everything will be questionable but put some very cum like substances on those same tits only pics and they'll be explicit

Aight, sick, thanks.