There are a few rules clarifications and significant reversals that the Rules Team decided upon earlier in the Kotei season and, by convention, did not release immediately in an effort to keep the competitive environment stable. Now that those events are over, we can clear these out and address several concerns players have had with unintuitive issues.
"opposing"
In all situations where it makes sense, this term still means "opposing this card". In cases where that interpretation cannot apply, its meaning is determined from context rather than always defaulting to the very general "opposing a card you control at any location". The exact meaning will vary from card to card, but generally, the interpretation will be "opposing the card performing this action." In addition, this will be restricted to the current battle only by the intent of the second major bullet point on page 81, since which card an ability is printed on is not the only factor that determines who performed it.
Primary example: Rain of Death's two abilities are now only useable by Tacticians at the current battlefield.
Unique, Singular, Loyal
These traits all impose restrictions against playing a card in some situations. Singular and Loyal also impose restrictions against a card coming under your control. Any effect that instructs you to bring a card into play or take control of one "ignoring restrictions" will overcome them.