it is hard to said, Geocities show yahoo's Ads. but you don't get pay from yahoo....hard to say... IMO just move it out, some hosting company is rather cheap..2.99 a month can get you decent hosting. As your site get bigger, Geocites won't be able to provide enough bandwidth
I don't understand but why wouldn't they like it? (though if you're serious about adsense, you should follow samskpunk's advice and get off geocities anyway)
I agree, I would say that is against TOS. Why get some paid hosting? If you can't afford it I can probably give you some for free, PM me if you want.
thing with free hosting sites is that they show ads. and putting your ads on the same page as their ads is against TOS. if u are really serious with adsense i think it's only wise that you invest in hosting to get a decent site. or get riboflavin's one.