Did another test with this code in header.php, which is shared by child/primary site:
switch_to_blog(25);
echo '<pre>';
var_dump(get_field('phone', 'options'));
echo '</pre>';
echo '<pre>';
var_dump(get_option('options_phone'));
echo '</pre>';
restore_current_blog();
exit;
(CHILD SITE)
string(12) “714 579 1642”
string(12) “714 579 1642”
(PRIMARY SITE)
string(2) “91”
string(12) “714 579 1642”