In a Postgres function, how to return the result of a query that is stored in a table?

Question

Initially let me explain the whole situation. The database is Postgres 13.

I need a "dynamic selection"

In the first place...

The tables I work with have many columns (approximately 200 columns). My goal is to create a function that takes the inputs: database schema, table name and the column range I want to use in "dynamic selection". For example, let's say I have a table called "customers" in a "public" schema and I want to list the contents of ordinal number columns between 20 and 50. I would simply call the function and the dynamic result would appear on the screen (something like select * from function(customers, public, 20, 50), internally the function would assemble a query something like this:

select column20, column21, column22, column23... column50 
from public.customers;

So, internally the function executes this query "select column20, column21, column23...column50 from public.clientes" and will return the result of it on the screen.