What law would be violated if you took coins from a mall fountain?

The law being violated will depend on the jurisdiction. It will vary from place to place. In places with no specific law, petty theft would probably be the charge. You can't really call change in a fountain abandoned property because it is contained in a fountain which belongs to some entity...perhaps a business which donates it to charity, or a municipality.

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Edit: Change left in a mall fountain is on private property and under the control of the landlord. It does not fit the definition of abandoned property.

It depends on how much coin you take, probably just a petty theft the coin is not yours and most fountains have a marker or plaque displaying the name of the owner or charity that is being donated to. It is possible to be charged with criminal trespass or even breaking an entering if the fountain is secured by rail or fence. Possibly disorderly conduct depending on how and who is present when you are stealing the coin.

Depends. If it is for a charity, then no. But if it is just a wishing fountain where people thrown coins in to make a wish (which those decorative fountains usually are...) then no, as that money doesn't belong to anyone.

Theft. You are taking money/property that does not belong to you. I don't know that the coins are considered abandoned. It could be they are considered a donation to the group maintaining the fountain.

It's a bad idea. The coins don't belong to you. Pretty simple.

If you're starving, go to a charity and get help.

The money is gathered up as a donation to charity so it's considered embezzlement.