can CSR be spent on floods !

Yes, company can spend as list provided under law is illustrative not exhaustive.

As per Sec.135 CSR Policy must indicate activities to be undertaken by the company as specified in Sch.VII and this Schedule does not cover natual calamities like floods.  Hence in my view it cannot be covered under CSR.  There is nothing in the Section to indicate that Sch.VII is just indicative.  Yes, contiribution to PM National Relief Fund is covered there.