Your question actually has me a little lost.
You can use get_field() for a top level repeater field, or any top level field.
get_field() should always return top level fields, not sub fields of any repeater or flex field. Using get_field() inside a repeater loop will not return values from the rows of a repeater. get_sub_field() shouldn’t get anything outside of the current repeater loop. If you are using get_field() inside a repeater then you’re probably not seeing what you think your seeing.
Here is some code illustrating a three level nesting of repeater type fields with comments about what will be returned where.
When I use get_field() or get_sub_field() this also refers to their equivalent function the_field() and the_sub_field().
// repeater loop
// this could be a flex field or a repeater
// both are treated the same as the loop is concerned
if (have_rows('flex_field')) {
while (have_rows('flex_field')) {
the_row();
/*
using get_field() here will not
return values from rows of the flex field
get_field() will still return values from
top level fields
you must use get_sub_field() to get values
from the flex field row
*/
// repeater in the flex field
if (have_rows('repeater')) {
while (have_rows('repeater')) {
the_row();
/* using get_field() here will still only
return top level fields not not value or
the flex field or this repeater
you must use get_sub_field()
it is impossible to get other values from
the flex field until after the end of this
loop get_sub_field() will return sub fields
of this repeater only
*/
// nested repeater
if (have_rows('nested_repeater')) {
while (have_rows('nested_repeater')) {
the_row();
/*
using get_field() here will still only
return top level fields and not values of
the flex field or the first repeater
you must use get_sub_field()
get_sub_field() will only return values
from rows of this nested repeater
*/
} // end while have_rows nested repeater
} // end if have_rows nested repeater
} // end while have_rows for repeater
} // end if have_rows repeater
} // end while have_rows for flex field
} // end if have_rows flex_field
