Reducing to the group of retaining 3 pairs and 1 1x2x2 block
Foreword
In the end, there is actually not many moves to choose from. To expand one of the completed pairs into a 1x2x2 block, it must be one of the colored 1x2x2 blocks below. The part with the X symbol is the 4 pairs that have been prepared before.
All the rotations of this step only rotate the R, U faces, and do not destroy the 4 pairs that have been completed in the previous steps.
4 pairs expand 3 pairs and 1 1x2x2 block
The following X part is the completed pair.
Combining edge and center
?
U R2 U' R'
0/4
Turn the edge out between the two old pairs
?
R' U2 R
0/3
The two pairs to combine block are on the same layer
?
R' U2 R
0/3
The two pairs to combine the block are not on the same layer
?
U2 R
0/2
Of course, you can also choose to combine another block first.
Combining edge and center
?
R' U R U2 R' U'
0/6
Turn the edge out between the two old pairs
?
U R2 U'
0/3
The two pairs to combine block are on the same layer
?
U R2 U'
0/3
The two pairs to combine the block are not on the same layer
?
R2 U'
0/2
Complete the Cube
When you have expanded into 1 1x2x2 block and 3 pairs according to the previous instructions, without destroying that 1x2x2 block and 3 pairs, there is only one way to turn, following that only way can be completed the cube.
Example
?
U R2 U' R' U' R' U2 R U R U R2 U' R2 U
0/15
Turn 1~4 is combined edge and center
Turn 5~8 is to expand 1x2x2 block
Turn 9~15 is the only way that does not destroy the pair and that 1x2x2 block. Follow that way to complete
