Your loan payoff will be on your closing statement. The fact that you are in arrears may be disclosed to the title company because they need to be aware that the payoff will change. The buyer will receive a copy of the title search (they probably will not read it) and that will show any public record filings. If there was a Notice of Lis Pendens filed, that would be included with the title report.

If you are less than 90 days in arrears or have otherwise mad arrangements with the mortgage company to not proceed to foreclosure, the buyer will probably never know.

No. The only thing the buyer SHOULD see is the total amount of the payoff involved to clear your mortgage fully. There should be no disclosure to anyone other than you, your lender, etc. concerning of what the payoff amount is comprised.