Take all forms fields names and labels, symfony 6

Question

I have one form. I wish to give to users option to set some of its fields as required. Is there good way to do this?

I tried to get all fields of form, but can't find fields of sub-elements.

 class DemandType extends AbstractType
{
 ...

    public function buildForm(FormBuilderInterface $builder, array $options): void
    {
        $builder
            ->add('client', ChoiceType::class, [
                'label' => 'Client',
                'attr' => [
                    'class' => 'form-control-sm',
                ],
                'label_attr' => [
                    'class' => 'label-form',
                ],
            ])
...
            ->add('demandFiles', CollectionType::class, [
                'entry_type' => DemandFileType::class,
                'allow_add' => true,
                'by_reference' => false,
                'required' => false,
            ])

}

Controller:

        $demand = new Demand();
        $formDemand = $this->createForm(DemandType::class, $demand);
        $arrayDemandFields = [];
        foreach ($formDemand as $childFormDemand) {
            $stringLabel = $childFormDemand->getConfig()->getOption('label');
                $arrayDemandFields[$childFormDemand->getName()] = $stringLabel;
        }
        var_dump($arrayDemandFields);

returns

['client'=>'Client', 'demandFiles' => null]

How to fix it? Or maybe there is another, better way to do this?

Thanks for your help.