Generally, yes you can; but it may not be what you want. Each INSERT statement will insert new rows into your table CUST. Any column in CUST for which you do not provide a value will be set to null. As long as that column is *allowed* to be null, the insert operations will work.
In other words, if CUST_ADD has 10 rows and CUST_INFO has 5 rows, your new CUST table will have 15 rows. Columns b, d, and e will be null on the first 10 rows and columns a and c will be null on the last 5 rows.
I'll let someone else talk about the lack of an index column, if necessary.