To get array of all meshes

Questions
2

You could do something recursive if the child has children of its own:

function listChildren(children) {
    let child;
    for (let i = 0; i < children.length; i++) {
        child = children[i];

        // Calls this function again if the child has children
        if (child.children) {
            listChildren(child.children);
        }
        // Logs if this child last in recursion
        else {
            console.log('Reached bottom with: ', child);
        }
    }
}

listChildren(scene.children);