Excel Cleanup: 200k Contacts

My phone book currently lives in a single .xlsx file and holds about 200,000 records. I need that sheet cleaned and standardised in two key ways:

1. Every duplicate number—regardless of whether it carries the +91 prefix or not—must be identified and removed so each contact appears only once.
2. Phone numbers must carry a consistent format for the Indian market. That means adding or stripping “+91” wherever required so each final entry follows one clear rule (I’m happy to agree on the exact rule with you before you start so we’re on the same page).

The end result I’m after is a fresh Excel workbook with:
• Zero duplicate rows
• Uniformly formatted mobile numbers
• No broken formulas, blank rows or stray characters

If you prefer formulas, Power Query, VBA, or a combination, that’s up to you—as long as the final sheet opens cleanly in Excel without additional steps on my side. Please let me know roughly how long the pass will take once I hand over the file and, if needed, what interim checks or sample outputs you’d like me to review before you run the full 200k-row operation.