Hello Sumeet,
you cannot use the input parameter directly within the string of the EXEC statement, because then it is interpreted as ":v_in_id".
You have to prepare the statement before. E.g.
DECLARE lv_statement string;
lv_statement := 'SELECT * from "BEST"."REGIO_TEMP" where "REGIO_TEMP_ID" = "' || :v_in_id || '"';
EXEC lv_statement.
But please consider that SQL injections are possible with that set up.
Best Regards,
Florian