I am just wondering who is the lawful owner of a property that is a under a contract for deed. Does the seller still own the home or does the buyer own the home?

The seller owns the home until they give a signed, witnessed and notarized deed to the buyer. A contract gives the buyer an interest in the home but not ownership.

That's why a contract for deed is better for the seller than for the buyer. The alternative is for the seller to take back a mortgage which means the property transfers ownership. In a contract, if the buyer defaults it's a lot easier for the owner to regain the property.

That is why of course it is called "contract" for deed, the seller owns and has the deed for the home in his name. The buyer merely has a contract that the seller will sign the home over to them when the terms of the contract is done.

Most contract for deeds converts to a rental if the buyer defaults in the terms

The seller owns the home until they give a signed, witnessed and notarized deed to the buyer. A contract gives the buyer an interest in the home but not ownership.

So, if anything happens in the house, the seller has to fix the problem? Say, the basement floods every time it rains. Does the buyer have to fix the problem, or does the seller have to fix the problem?

That depends on what's in the contract. Some (probably most) contracts say that the buyer will take care of all repairs and maintenance. If your contract doesn't say anything about repairs then you can probably make a good case for the seller being responsible.

No we did not say that, you only asked who legally owns the house.

You are buying the house, so what does the contact say as to who has to fix things, it can vary by contract,

In all of my contracts ( I am normally the seller) the buyer has to pay all the taxes, pay for property insurance and is responsible for any and all up keep. Since they are buying the home.

This is why you always get a good inspection done before you sign the contract.