css and/or SASS + (sibling) selector upwards [duplicate]

Answer 1

May or may not be suitable for your needs but you can use the general sibling selector in Sass/CSS. This will select all elements on the same node level (not explicitly before but still handy):

.second {
   .first ~ & {
       /* styles to be applied to .second if a .first exists at the same node level */   
   }
}