Module development and code questions

We are currently experiencing garbled characters in the subject of emails sent from our Drupal site.
Garbled characters occur when we enter the email subject in Japanese characters with more than 257 bytes.

To clarify this issue, I have the following questions about email subject specifications when using contribute module "webform".

・Is there a specification for email subjects?
・Is there an upper limit on the number of characters or bytes that can be set for an email subject?

I'd appreciate it if you'd cooperate with me.

If I crate the class for test like:

class ReturnHandlerTest extends OrderKernelTestBase
{
    protected static $modules = [
      'commerce_payment',
      'commerce_payment_example',
    ];


    protected function setUp(): void {
        parent::setUp();
    }
}

And if I want to use

 Url::fromRoute('commerce_payment.checkout.return', $arguments)
            ->setOptions(['absolute' => true])
            ->toString()

In the test, I get this exception.

how do I remove the word "title" from the products in the shopping cart?
I have Drupal 7.92 if that helps

Hello I have a custom form with 2 date fields
In the submit I run a query that returns an error when I don't enter the date
I found a solution but I don't know if it is the right solution and if it is ok to operate like this
Below is the code

FORMBUILD

I am using the following hook_views_pre_render to merge 2 views_data_export views.