Walking
 

The claim – This is the longest road a man can walk.
22387 km, 13,911 miles, 4492 hours(3.1 mph), 561.5 days @ 8 hrs/day

I doubt it’s a single road but it is sort of straight, kind of.
Cape Town to Magadan, Russia, which is on the sea of Okhotsk still 4 or 500 miles from the Kamchatka peninsula
and the Bering Sea, but maybe no roads. More crooked could be a lot longer, but no matter ‘cause I ain’t doing it.
I wouldn’t even drive that “road”.

I wonder how difficult all those borders would be?

You can certainly walk a much longer distance than this route by zig-zagging around and making detours.

It looks like the rule for this "road" is that it is the longest walking distance between two points using the most direct walking directions Google gives you.

I doubt it. If he was walking through Syria or the Sudan border region, he would probably be dead. He was probably doing a lot of running.