You are always able to deduct the property taxes on both properties.
You can also deduct the mortgage interest on your principal residence. You are also allowed to deduct the mortgage interest on a second home.
There are limitations on the amount of interest deductible. The total amount of home acquistion debt cannot exceed $1 million. There are other limitations. I have provided a link to IRS Publication 936 that explains the limitations in greater detail.
Yes, all property taxes can be deducted.
The $1 million applies to the total allowed amount combined for both residences.
If the returns were done incorrect in prior years, you can amend returns going back up to 3 years.