Salesforce Classic Edition Security Enhancements

Sales Force Security enhancements - 25.9.24

Below a brief on my outline requirements. I am open to suggestions on how to implement additional security required.
I am looking for a fix fee for the project.

We use Salesforce Enterprise Edition working in Classic
We have the 2 Orgs - its the Classic version we use.
We have 3 user profiles:
• Systems Administrator
• Sub Administrator
• Engineer
All users currently have access to All pages.
We need to restrict access to all but Live Opportunities
If the project is a live job, the Stage is either:
• Contract won
• Closed Won
• Site Advice Visit Completed
• Consultancy Report Ready
• Testing Report/s Approved For Sending

The Opportunity Page has required information with look up fields related both the Account and Contact Pages
We are looking to limit Engineer and Sub Administrator access to all information unless the Stage is as specified above
We require an ‘Over ride’ button if the stage is other than above there need to be a tick box (or similar) on the Opportunity that enables the user to view that Opportunity.
The restrictions above also need to limited the information which is available on reports e.g so the user can not report on an export information

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