>1. where do i find the documentation and syntax for these statements.
They are documented in the HANA Developers Guide:
Although I would recommend the use of the HDBDD format instead of HDBTable:
The HDBTable is still available for backwards compatibility but won't receive further development. Its replacement is HDBDD/CDS.
>2. can we use usual SQL statements instead of these statement in .hdbtable file.
Sure you can use SQL Statements (like CREATE/ALTER TABLE), but you give up the ability to transport via Delivery Unit, lifecycle management of the data in the table during changes, and all the other benefits that go with design time creation of tables.
>3. these statements are used only for table creation or for all SQL operation (CRUDQ)...
The above syntax is just for the design time definition of a table.