how to select the specific column without knowing column names

I am new to SAP HANA as developer. I am in a situation where I have no idea what data is going to be input by users and I want to go through the cells of the table provided by users. In order to achieve that, I would like to select any column by referring to their positions in table.

The code is

/*Creation of table*/

DROP TABLE TEST_TABLE2;

DROP PROCEDURE TEST_TABLE2;

CREATE COLUMN TABLE TEST_TABLE2 (X INT, Y INT, Z INT);

INSERT INTO TEST_TABLE2 VALUES (1,2,3);

INSERT INTO TEST_TABLE2 VALUES (4,5,6);

INSERT INTO TEST_TABLE2 VALUES (7,8,9);

INSERT INTO TEST_TABLE2 VALUES (10,11,12);

DROP TABLE TEST_TABLE2_PROPERTY;

/*Creation of table containing column names and position*/

CREATE COLUMN TABLE TEST_TABLE2_PROPERTY AS (SELECT COLUMN_NAME, POSITION FROM TABLE_COLUMNS WHERE SCHEMA_NAME = CURRENT_SCHEMA AND TABLE_NAME = 'TEST_TABLE2' ORDER BY POSITION);

/*Attempt to extract column number 2 in TEST_TABLE2, which should be column Y*/

SELECT (SELECT COLUMN_NAME FROM TEST_TABLE2_PROPERTY WHERE POSITION = 2) FROM TEST_TABLE2;

The expected output is a table with only column Y of TEST_TABLE2, but the weird output comes up

Could anyone help explain why such weird output what should I do to get desired output?