Request for Support - CRM Integration Issues

I’m reaching out to request assistance with the following items:
1. Zoho Forms Integration with Zoho CRM

We are currently using Zoho Forms to send the Global Credit Application form to our customers. The intended workflow is for the form submissions to automatically update the customer’s contact details (e.g. phone number, email address, etc.) in Zoho CRM. However, we've encountered a few issues:

Submissions are creating new accounts even when an existing account is already present.
The ABN field, which was recently added to autofill the GST/VAT number in CRM, is not updating consistently.

Missing Data in CRM
We’ve noticed recurring missing fields such as Industry and Account Type were for the accounts newly created. How can we ensure these fields are consistently filled moving forward? Additionally, is there a way to track who is responsible for these incomplete entries?
Data Access Monitoring
Is there a way to view who outside of our organization may be accessing our database? How to avoid someone from accessing our database outside our organization.

Thank you in advance for your support. Looking forward to your guidance on these matters.