penalty enforcement -line to gain

[pinchmaster]

Hi friends, newbie here.I have a question about enforcing penalty when penalty is past line to gain. 2ND and 10 ,run play,handoff to A1 ,gains 40 yds. Flag is thrown for holding near the end of run. Flag is spot of foul,mark back ten yards,ball is still 25 yards beyond l to g .Is it a first down even on a penalty? (high school)What about a block behind the back in same situation.The more I read my book the more confused I get.