Hi Kabeer,
You must have a S-user in the website service.sap.com in order to download SAP Sofware. You need being a SAP customer to have access to this website.
It depends on the license you get from SAP so you can download Oracle database or MS SQL or whatever. Not all the customer are able to download Oracle software from SAP service.sap.com.
There is a SAP ECC IDES version that is prepared for testing purposes. It's not a trial version, it is a testing environment with data.
Hope this helps.
Best regards,
Martina