How to see tables and column names in exact case which is created and not by default uppercase?
That has nothing to do with TOAD. 

As documented in the manual Oracle converts all non-quoted identifiers to uppercase. 

If you really, really want to make your life a lot harder then it has to be, and really want to create mixed case identifiers, you have to quote them during creation:

create table "SomeTable" 
(
   "Id" integer not null primary key,
   "SomeColumn" varchar(100)
);


But I strongly recommend to not use quoted identifiers. They will create much more problems in the long run than they are worth it.