How to let an existing user buy a subscription without signing in?

  1. How can an existing user continue buying a subscription using the same email ID without signing in?

    I have made the new user to create a password at the end of the checkout/purchasing the subscription. I want even existing users finish the checkout without signing in/verifying the email ID. Later, they should be able to access the subscription with that email ID.

    Why? Because, there's a chance that they might forget the password which may result in drop-off's

  2. What if user enter wrong email ID during checkout? How can he get his subscription back into his account?