The type for the div jsx element is HTMLFactory<HTMLDivElement>.
The reference you have isn't for an actual dom element in the browser but for a react element which represent such an element which might not be rendered yet.
The html properties should be accessed through the props:
let element = <div>Blah blah</div>
console.log(element.props.accessKey);
If you'd like to get the dom element you can use the ref attribute:
When the ref attribute is used on an HTML element, the ref callback
receives the underlying DOM element as its argument
So:
let divElement: HTMLDivElement;
let element = <div ref={ (el) => { divElement = el; console.log(el); } }>Blah blah</div>
In the case of the imported Row, again, you have a reference to a react element which has a dom representation.
Which properties or methods it has depends on the class itself.