Questions about (almost) 3 month old?

My baby girl will be 3 months on Thursday. I get help through WIC and I think they told me when I go back in November to get my vouchers I can start giving and buying my baby cereal. I thought they weren't suppose to get this until they were 4 months? Also, when could my baby start to roll over and sit up? Sometimes she tries to roll over but she quits after awhile . When did your baby(ies) sit up/rollover?