running bases in reverse order

[walkerbard]

I have question RE: this scenario but this
time it is the BATTER/RUNNER between HOME
and 1st. Batter hits slow grounder up 1st
base line that is fielded by the pitcher
who intends to tag batter/runner out. Meanwhile,
runner on 1st (R1) heads for 2nd. Batter/runner
stops to make pitcher come towards him to
buy time for R1 to make it safely to second.
Batter/runner then backs up towards home to
buy MORE time/distract pitcher so R1 MIGHT
continue on to 3rd. Does the fielder have
to tag out/throw to 1st or is the batter/runner
called out immediately when his forward motion
towards 1st stops/reverses? If he is called
out, perhaps that is what the ump in the original
question here was thinking and applied.