Stage 4a. Orient remaining 6 edges
Objective: Make it so all remaining edges have either white or yellow facing up and down.
restrictions: no down layer moves, no left or right moves.
What we can move: After we use the M slice to move a yellow or white centre to the upper layer the M slice will me limited to M2 moves. The upper layer can be rotated any way we need and a few Algs
Method: The first thing we have to do in this step is to move a yellow or white centre to the upper layer via the middle slice. After we have a yellow or white centre on the upper layer. The M slice will only be able to move with a M2 or we will lose our centres. Now we look at our last 6 edges to find out how many bad edges or good edges we have. A bad edge is any edge that doesn’t have white or yellow facing up or down. A good edge is either white or yellow facing up or down. The number of bad edges is always even. There is either zero bad edges, 2 bad edges, 4 bad edges, or 6 bad edges. The way we orient the edges is to use a mini alg M* U* M*. We rotate the upper layer to match diagram then use M* U* M*. Then adjust upper layer to match diagram then do alg again. We keep doing this until we have the arrow pattern. The arrow pattern is exactly 3 bad edges on top and one on the bottom. When we get this pattern we adjust the upper layer so the arrow (triangle) points toward the bad edge on the bottom. Then use the middle slice to move the bad edge on bottom to the top layer then do any random U move followed by any random M move to orient edges. All colours on the upper slice should now be either white or yellow and the down slice should be the same either white or yellow.
Stage 4b finish left and right sides
Objective: Place yellow/green edge and yellow/blue edge finishing the left and right sides.
restrictions: no down layer moves, no left or right moves M* and M.
What we can move: M2 moves are still allowed. The upper layer can be rotated any way we need and a few Algs
Method: The first thing we have to do in this step is to locate the green/yellow edge and the blue/yellow edge. After we locate them we need to move them so that one is on the upper layer and the other is on the down layer. We can then rotate the upper layer so that both edges are on the middle slice and on opposite sides from each other. SO if the bottom edge is at the front the top edge must be at the upper back position and if the edge is on the down back position then the other one must be in the upper front position. Now we do this special alg. Bare with me this will take a while to explain. M* U2 this will stack the two edges on top of each other. Now we use the middle slice to place both edges on the bottom layer. We now look at the colour that is facing us on the down slice. It will either be blue or green. We now have to adjust the upper layer so that the headlight of the opposite colour is on the same side. Now we do a M2 which will insert our edges into the proper headlights. Now all we have to do is rotate the upper layer so we complete the left and right sides.
After positioning the yellow green and yellow blue edge peice so that one is on top layer and the upther in on bottom And have them so the are diagional from each other (aka one at front the other at back) . Use this special adjustment alg to solve the left and right faces.
Stage 4c. Orient remaining middle slice
Objective: Make it so all remaining edges in the middle slice are sovled
Restrictions: no down layer moves, no left or right moves. No U or U*
What we can move: After solving the left and right edges in step 4(b). We have limited the upper layer to U2 moves only. In effect every M move will be followed by a U2 move until the end of the solve.
Method: The first thing we have to do in this step is to locate a two bar pattern and move it to the upper layer. If we do not see a two bar pattern on the upper layer we will do a U2 to get one. After the U2 the two bar pattern will be on the front middle slice. We will do a M* to move this pattern to the upper layer. Then do a U2 (the only U move we can do at this time). So now we have the two bar pattern on the upper layer all we do is move the side with 2 colours down with an M move then do a U2. IF the 2 colours are at the back move the M slice to move the pattern to the back Then U2. If the two 2 colour is at the front move the M slice to move the pattern to the front then U2. Then repeat with the 2 bar that appears on upper layer again. Rinse and repeat until there is a 3 bar line on front and upper layers. We simply have to rotate the middle slice until the colours match. Congratulations you have just solved the Rubic’s cube.