Copy and re-customize my existing custom Wordpress registration plugin

I need a form requesting users personal info such as name, shipping address, email, confirm email, and password followed by drop box to choose an order source: (Amazon, Etsy, etc), and a text field for Order #. Below that I need scroll window (iframe) for our terms of service and a drop box menu with 3 options: Service Animal ID, Emotional Support Animal ID, Therapy Animal ID. Upon the user making a selection in this drop box, a form will appear below it with the fields that they need to fill in. If they choose Service Animal ID, the form will have the following fields: Dog Registration ID: <------- This is an auto-generated number 10 digit number that the user can't change Name * Dog photo * Handler Name * Handler Photo (optional) DOB of Dog * Primary Function * Medical Condition (optional) If they choose Emotional Support Animal ID or Therapy Animal ID, the form will have the same fields as above plus 2 extra text fields. Above the form there will be a picture of a generic ID card and when the user is filling in the form fields, the card above it will auto-populate what they are typing on the card. See the following video as an example of what I mean: [login to view URL] Below the form I need a "Finished" button and a "Create another ID". If the customer clicks "Create another" they will be shown drop box menu with 3 options again: Service Animal ID, Emotional Support Animal ID, Therapy Animal ID. Upon the customer making a selection in this drop box, a form will appear below it with the fields that they need to fill in just like before. This lets them create as many ID cards as they want and then they can click the "Finished" button when they are done. We are currently using a custom plugin that has a similar registration form and once the registration form is filled out, all of the data is saved on the site and can be searched for (it is a dog registry website). I need this new registration process to work with our existing one so basically you can use the registration plugin that we have now and modify it so that it works as described. The current plugin already generates the 10 digit ID and it also registers the users and their dogs to the database so some of the work is already done for you. Lastly, upon the user clicking "Finished" I will receive an email with with any pictures attached. The user will receive a copy of the email, and their details will be stored on the site in the same way as if they would filled out our existing registration form. I need to be able to modify the email messages on the backend that is sent to the admin and to the user such as being able to use the order number and type of ID ordered in the subject line. Basically we are redoing our current registration form to look a little nicer and easier to fill out so much of the programming has already been done on our site. Please message me if you would like to see our current registration process.