[KWH]

Answers
Situation A:
1) If the R captain accepts the K penalty, then the K captain will undoubtably accept the R penalty creating a "double foul" and the penalties will offset.
2) If the R captain declines the K penalty, then the K captain will undoubtably accept the R penalty, if this is the case then PSK applies. Since the kick ended at the R15, this becomes our new basic spot. The 10 yard holding penalty is enforced from the R15 (Half the distance applies) and the result of the play is 1st and 10 for R at the R7 1/2 yard line.

Situation B:
PSK is not applicable during this play because the R foul DID NOT OCCUR during the scrimmage kick, rather it occured after the scrimmage kick had ended.
1) If the R captain accepts the K penalty, then the K captain will undoubtably accept the R penalty creating a "double foul" and the penalties will offset.
2) If the R captain declines the K penalty, then the K captain will undoubtably accept the R penalty, if this is the case then the "All but one principal" applies. Since the foul occured during a running play the end of the run becomes our new basic spot. The 10 yard holding penalty is enforced from the R22 and the result of the play is 1st and 10 for R at the R12 yard line.

Situation C:
PSK is not applicable during this play because the R foul DID NOT OCCUR during the scrimmage kick, rather it occured prior to scrimmage kick.
You however failed to give the result of the play. For this reason I will assume then that R7 fielded the ball and returned it for an apparent TD.
1) If the R captain accepts the K penalty, then the K captain will undoubtably accept the R penalty creating a "double foul" and the penalties will offset.
2) If the R captain declines the K penalty, then the K captain will undoubtably accept the R penalty, if this is the case then the "All but one principal" applies. Since the foul occured during a "loose ball play" the previous spot becomes the basic spot. The 10 yard holding penalty would be enforced from the previous spot and the result of the play would be 1st and 10 for K on the K45.

I hope this helps