Required Zoho Creator freelancer for Zoho Custom Application Development job

Background:
Our former CTO built a custom application that streamlines our payment processing activities. This is how the application works: On Zoho Creator, our internal employee fills out a few fields (including name, email, invoice amount, and service type). He submits this form and an invoice number is automatically generated. We provide that invoice number to our customer, who inputs this number on a public-facing URL. All the information associated with this invoice number is automatically populated on this public-facing page. The customer then chooses his first payment date and signs the page (there is a Zoho Sign widget on this page). He is then taken to a Zoho Checkout page, where he can fill out his credit card information and process payment. All the billing data is transferred to Zoho Subscriptions for internal management.

There was a field on the public-facing URL called 'Decision Box' that was not necessary. I called Zoho's customer service to remove it, and they did (it was referenced on 3 different scripts). Ever since it was removed, the application does not work. The error I'm getting is 'Error details: Error occurred please contact application owner.'

Requirements:
1. Fix this error so the payment portal works.
2. On the public-facing URL, there is a drop-down field that is auto-populated with the customer's name. I'd like for that to be changed from a drop-down, to a static field. As of now, the drop-down options have all the name's of everybody that has ever used this application.
3. On the public-facing URL, the Price field is editable. I need it to remain fixed, so a customer doesn't have the ability to change the price that was agreed upon.
4. On the public-facing URL, there is a terms of service text box. I need it to require the customer to scroll through the entire terms of service to proceed. If he doesn't scroll through it, it doesn't allow him to proceed and prompts him with a notification to read the entire terms of service.
5. All the information on the pubic-facing URL (that's populated with customer's details), needs to be sent to an email as a receipt, so it can serve as a legally-binding contract. The information that needs to be auto-sent are: name, amount, payment frequency, terms of service, approval to process recurring payments, and signature with corresponding auto-generated key (provided by Zoho Sign). We need this information so if a customer ever disputes a charge, we can provide corroborating documentation that supports that the transaction is in fact valid.

I expect to review the issues and requirements via screen share with the chosen candidate.

Thank you for your time and consideration.

Skills & Expertise Required

Zoho Creator