When is a baserunner not protected after reaching first base for example after a batter-runner safely reaches first base and turns in foul territory when is he no longer protected?

Answer 1

After a batter has hit a ball and runs to first base he is allowed to over run the bag (base) ... If the base runner turns left in the siltiest way it is seen as if his going for 2nd base (even if he walks back to first) he can be tagged out ...