Hi Aravinth,
As you are currently working on BASIS then go for C_HANATEC_1 certification as it is more on administration part of HANA like installation and system architecture
But as you said you have joined OpenSAP course and you feel comfortable in coding then you should go for C_HANAIMP_1 certification as it relates to developing Models, Reporting and Provisioning in HANA
You can get most of the documents form : http://help.sap.com/hana_appliance/
Visit SAP HANA Academy for Video Tutorials : http://www.saphana.com/community/implement/hana-academy
Check these links for SAP HANA Certification: SAP HANA and In-Memory Business Data Management... | SCN
SAP HANA and In-Memory Business Data Management... | SCN
SAP HANA and In-Memory Business Data Management... | SCN
And finally Get your hands on HA100 or HA200 and HA300 books
But first of all decide whether you want to go for Technical Certification or Developer one