You are returning false right before your header statement.
return false;
header ("Location: /");
Should be
header ("Location: /");
return false;
EDIT Just realized your if statements are all wonky. Change them:
if($step2 == 0)
{
header("Location: /steptwo");
exit();
}
if($step2 != 0 && $vpic == 0)
{
header("Location: /idupload");
exit();
}
if($step2 != 0 && $vpic != 0 && $act == 0)
{
header("Location: /pending");
exit();
}