I got strange redirects with Inertiajs errors on data post submitting

With Laravel 9/Inertiajs 3 I have home page with code in control :

return Inertia::render('Frontend/Home/Home');

In modal form (with "vue-final-modal": "^3.4.3") I made User register form as wizard with several steps and when user submit details form

1. I run sendUserRegisterStep1 function with code :

    <div class="content frontend_modal_content_editor_form frontend_modal_content_wrapper"
        v-show="user_register_wizard_step === 1">
         ...
         <input type="text" class="form-control" id="modal_user_register_name"
             v-model="formUserRegisterEditorStep1.name" maxlength="100">
         <div class="fs-error mb-3" v-if="formUserRegisterEditorStep1.errors"
             :class="{ 'd-block' : formUserRegisterEditorStep1.errors && formUserRegisterEditorStep1.errors.name}">
             {{ formUserRegisterEditorStep1.errors.name }}
        </div>
    </div>
    ... 
    function sendUserRegisterStep1() {
        console.log('sendUserRegisterStep1::')
   
        formUserRegisterEditorStep1.value.post(route('user_register_step_1'), {
        preserveScroll: true,
            onSuccess: (resp) => {
            user_register_wizard_step.value = 2 // Open next step form
   
            formUserRegisterEditorStep1.value.id = resp.props.user.id // Pass parameter next steps form
            formUserRegisterEditorStep2.value.user_email = formUserRegisterEditorStep1.value.email
            formUserRegisterEditorStep2.value.user_id = resp.props.user.id
            userRegisterAvatarUploader.value.user_id = resp.props.user.id
            userRegisterAvatarUploader.value.user_email = resp.props.user.email
   
            new_registered_user_id.value = resp.props.user.id
            new_registered_user_email.value = formUserRegisterEditorStep1.value.email
   
            Toast.fire({
                icon: 'success',
                title: 'You have registered successfully. Check your email with confirmation code'
            })
        },
        onError: (e) => {
            console.log(e)
        }
    })
   

   } // sendUserRegisterStep1

and control action :

public function register_step_1(RegisterStep1Request $request)
{

    $newUser= null;
    try {
       // NEW USER CREATION CODE
    } catch (QueryException $e) {
    ...
    }

    // I suppose lines below raise problems
    return Inertia::render('Frontend/Home/Home',
        [ 'user'=> $newUser]
    );
} // public function register_step_1(RegisterStep1Request $request)

I the method above I can not return response()->json(, As I got error : All Inertia requests must receive a valid Inertia response

when data are valid new user is created but url of my site is changed from home page

http://local-bi-currencies.com/

into post url

http://local-bi-currencies.com/register_step_1

as in routes I have :

Route::post('/register_step_1', [AuthController::class, 'register_step_1'])->name('user_register_step_1');

I think returning lines

return Inertia::render('Frontend/Home/Home',

are invalid, but I do not know which way can be used here?

1. On the second step I have similar form where user must enter confirmation code send by email. Having similar control with custom request :

    public function register_step_confirmation_code( UserRegisterConfirmationCodeRequest $request)
    {
        ...
        $user->status= 'A'; // active
        $user->confirmation_code= null;
        $user->save();
        // And again I need to return some inertia responce...
        return Inertia::render('Frontend/Home/Home',
            ['user'=> $user]
        );
    }
   

when entered data are invalid and UserRegisterConfirmationCodeRequest with custom rulke :

public function rules()
{

    $request = request();

    return [
        'confirmation_code' => 'required|min:8| ' . 'check_valid_confirmation_code:' . $request->confirmation_code . ','
                               . $request->user_email . ',' . $request->user_id
    ];

and check_valid_confirmation_code defined as :

Validator::extend('check_valid_confirmation_code', function ($attribute, $value, $parameters, $validator) {

    $confirmation_code = $parameters[0] ?? null;
    $user_email        = $parameters[1] ?? null;
    $user_id           = $parameters[2] ?? null;
    $user = User
        ::getByEmail($user_email)
        ->getById($user_id)
        ->first();
    \Log::info(varDump($user, ' -12 check_valid_confirmation_code $user::'));
    if (empty($user)) {
        return false;
    }
    \Log::info(varDump(-13, ' -13 check_valid_confirmation_code ::'));
    // Checking log file I see that  line above  was written
    if ($user->confirmation_code != $confirmation_code) {
        return false;
    }
    // But line below WAS NOT WRITTEN
    \Log::info(varDump(-14, ' -14 check_valid_confirmation_code ::'));

and I get very strange GET request at

http://local-bi-currencies.com/register_step_1

and error as I do not have such GET request in my routes.

I try to use inertia in somewhat uncommon way(At least I did not find methods in docs I cxan use here). Are the some usefull methods?

I know how axios works in such case, but I do not want to use it, as I want to keep laravel validation/errors in my app. I suppose I can not use

{{ formUserRegisterEditorStep1.errors.name }}

with axios request.

How that can be salved ?

Thanks!