[Tyhm]

Two things:
One, if you make a map that links like that, you can't See 3 from 1.
Two, if you revise the map to be
97897
31231
64564
97897
31231
You have at least two copies of every level, confuse the hell out of the game - but at least you can see the next level if you're lucky enough to be in the Middle Nine.
Three, If you make actual copies of the edge levels, ie
ighig
c123a
f456d
i789g
cabca
you can see the Tiles of level 9 and 3 and 7 from 1 (reflected in their clones, levels g and c and i), but you can't see the PKer that dashes across the World Edge to slash at you and then dashes back.
Further, in none of these situations can you shoot an arrow over the edge of the world and have it wrap, etc.

Four, spaced intentionally, TheWorldIsSquare. Only on toroid (donut-shaped) planets can you both travel so far to the east that you wind up at the west AND travel so far to the North Pole that you find yourself at the South Pole. Assuming you want a Classroom Wall map, where you go north from Canada and find yourself in the Former USSR, or where you go cross Antarctica and go from South America to Australia. In such a case you either need a world where you can rotate every level north-to-south so someone can continue going "Forward", or a special case for If you go off the north side of the planet, turn around and be warped (1/2 the width of the planet in levels) to either side.

And yes, I did plan on using such technology for Classic, so of course I know these things. :-P