Please recommend a Linux SBC with Industrial stability while it is made in ABC?

Border router has a special meaning, I doubt that's what you actually want (if you are, then a typical SBC is going to be very inadequate).

There are ready-made, packaged, small edge compute devices, some of which are intended for industrial deployments. You'd be better off using one of those, even tearing them apart and repackaging them if necessary (some industrial users tend to do that), since they usually run Linux under the hood, and many of the modern ones will allow you to run either a container or perhaps a full virtual machine with your software.

Otherwise, another option is to get a custom SBC made to your specs. Raspberry Pi and/or Avnet offer this service. An example is a Hilscher product called netPi, it's an industrial device with custom Pi in it, although it was discontinued last year. However, they offer an alternative product called netFIELD: https://www.hilscher.com/products/edge-gateways-with-container-management/edge-gateways/nfx8m-d2-n32-010

You can run your own software on it, since it supports containers. I don't know if it has an LTE interface (or if it could be added as a plug-in module) but there are other ready-made devices out there with LTE.

Raspberry Pi make the 'Compute' module which I believe is used in various industrial-grade PLC's and the like. I don't know much about it as a) I've never had cause to use it, b) the last company I worked for made their own PLC look-alikes, and c) I havn't worked in industry for several years as I am retired. The information is on the Raspberry Pi web site, it might be worth a look. But reading between the lines it looks as if you might be needing military spec devices at vast expense, and I don't think the Compute module qualifies.

It's often things like crystal choice which can make the difference and some other components might operate at higher temperatures when tested. As well as the compute module, Avnet also offer a complete custom service (in conjunction with raspberrypi.com as I understand) where they will drop the Pi design directly onto a PCB. Hilscher did that with Avnet (I think). The photo below isn't high-quality, but the Pi 3 portion is visible at the lower-right. Since it was a custom design, they were able to add plug-in functionality, like interfaces (don't know if they had LTE, I think they didn't, but they were thinking of opening up that port so that users could create their own plug-on boards). But it's now obsolete (I think due to part obsolescence), and they suggest the netFIELD product now.

I think if the OP finds the closest industrial product that meets his needs (there are dozens of industrial computers and routers, and nearly all will support custom applications), he should talk to the manufacturer, who will probably be more than happy to advise how to further ruggedized and improve the temp spec to meet a need. If he has money to spend, then Avnet will design him one based on a Pi.

It's often things like crystal choice which can make the difference and some other components might operate at higher temperatures when tested. As well as the compute module, Avnet also offer a complete custom service (in conjunction with raspberrypi.com as I understand) where they will drop the Pi design directly onto a PCB. Hilscher did that with Avnet (I think). The photo below isn't high-quality, but the Pi 3 portion is visible at the lower-right. Since it was a custom design, they were able to add plug-in functionality, like interfaces (don't know if they had LTE, I think they didn't, but they were thinking of opening up that port so that users could create their own plug-on boards). But it's now obsolete (I think due to part obsolescence), and they suggest the netFIELD product now.

I think if the OP finds the closest industrial product that meets his needs (there are dozens of industrial computers and routers, and nearly all will support custom applications), he should talk to the manufacturer, who will probably be more than happy to advise how to further ruggedized and improve the temp spec to meet a need. If he has money to spend, then Avnet will design him one based on a Pi.

Thanks for that nice photo.

I am also considering something like this after having read your comments.

I will start with Pi Compute IO Board and AVNET MAXX Board.  

I also think that a grounded metal case is crucial for stability.