Confused on 4th down OPI

[Refsmitty]

Situation is 4th and 10... A is called for OPI - pass is incomplete... if B declines the penalty do they just get the ball due to turnover on downs or do they also get the 15 yard penalty for the OPI.

I am thinking they just get the ball and the 15 yards and loss of down is not an issue.

What if the pass was complete for a first down and OPI was called? I think that B get the ball by declining the penalty - now a turnover on downs - correct?

I am unable to locate that sit in case book