You want an explanation of how the border will work after we leave 59 ? I can't give you an answer, I am no expert on how any borders work, I have no idea even on how it works now, and more to the point, it's not my problem. The backstop is only in operation until we agree a trade deal, so both sides agree therein lies a solution, you can either believe them or not, up to you. I really wouldn't know and am beyond caring.
The EU has encapsulated Article 50 in it's Treaty of Rome, this gives us the legal right to leave the EU, either with a withdrawal agreement or without one, thus we are leaving the EU in one of two ways, both of them perfectly acceptable to the EU, they are their terms and we will be leaving fully in accordance with them.
Our government offered us a choice, our parliament passed the legislation for the EU referendum, thus confirming that they agreed with us having that choice. We voted to leave, our parliament then passed the laws necessary for us to enact the decision to leave, both major parties stated in their last manifestos that they would honour the result of the referendum. So we are where we are now because of decisions taken by politicians, bureaucrats and civil servants in both Brussels and London, and with the full agreement and confirmation of both the EU and our parliament, everything has been done by the book. If this presents an apparently insurmountable problem on the Irish border, then it's their doing, not mine, it's their problem, not mine, it's up to them to find a solution, not me. There are thousands of them 59, employed at my and your expense in London and Brussels, paid to solve these problems, they have given us a legal means to leave the EU, and we are taking it, when we do leave on October 31st as we are legally entitled to do, obliged to even, under The EU's Treaty of Rome Article 50, I have every confidence that these massively expensive bureaucracies on both sides of the channel, will rise to the challenge and suddenly find an answer to this confected problem, it's what we pay them for after all isn't it, but it's not my problem either way, and I won't be losing any sleep over it.