NCAA 4th Down Fumble Rule
 

On 4th down, there is a fumble that is recovered by an offensive player other than the fumbler. He advances three yards where he fumbles. This time, it's recovered by the defense.

Does the defense get the turnover, or do you have to revert back to the ball being dead at the time of the recovery by the non fumbling player?

The second fumble did not occur. The ball is dead when the recovery is made by the other team-A player.

The ball is either returned to the spot of the fumble or to the spot where the fumble was recovered should that had been behind the spot of the fumble.
If the line to gain was been made.. then first down, else the ball is turned over to team-B.

So this ruling is different than the NFHS ruling would be, right? (I'm thinking 7.4.2 and am a 1st year trying to make sure I have the rules right.)

There is NO fourth down (or TRY down) fumble rule in NFHS rules.

Do not blow the ball dead when recovered by any team-A player or team-B player unless of course the recovery was while he was down. Let the down continue until the play is over by rule.

We, NFHS, get to let the play go until the ball is dead. Just be sure to watch for the illegal bats and kicks on this play.