Can a loan for a one acre lot be put on an installment note? Is there something in a regulation that states acreage above or below a certain amount can be on an installment?

There is nothing in the regulations. State law may be a different matter, but not in Florida.

Usually the defining terms here are what the customer can repay and the schedule you, the lender, will accept.

To be clear, when you say installment note, you mean payments? Some lenders I have heard refer to "installment" as in "consumer", vs. commercial or real estate.

As noted, check your state laws and your internal policy.