Hi @mohammadz,
You can continue to use the Classic Universal Login Experience for this flow! In your Universal Login template (from your dashboard, Branding > Universal Login > Login tab), if you are using Lock, you can make sure that the signup option will not be displayed by using the allowSingup setting.
You can either create a password-change ticket, or you can use the Management API to send a password change email instead. You can customize this email to look like a welcome email by configuring an email provider (Branding > Email Provider) and customizing the “Change Password” template (Branding > Email Templates). You will need to disable the welcome and verification email for this flow which you can do from the Email Templates settings.
In this topic, I break down the steps for invite-only flow:
Also, here is a guide from our documentation that covers an invite-only flow: