Help - ink and unidentified flying food stains

bluep

I just bought some baby clothes on ebay that turned up stained. The seller has given me a partial refund and told me to keep the clothes....and I really like the design of them. Any ideas how to remove:
a) what looks like blue ballpoint ink (not thick enough to be marker)
b) unidentified light yellow stains (probably food)
c) what looks like yellow/brown banana (I've got similar on our baby clothes and still can't get it off)

I know its likely that these clothes have already been washed - has this "set" the stain for good? What about washing them in really really hot water? Any ideas? I'm determined to give it a good go before consigning them to the rubbish bin.