Prelims
a) R12C5 = {29/38/47/56}, no 1
b) 17(2) cage at R2C3 = {89}
c) 6(2) cage at R2C7 = {15/24}
d) 16(2) cage at R3C2 = {79}
e) R34C5 = {14/23}
f) 11(2) cage at R3C8 = {29/38/47/56}, no 1
g) R5C67 = {89}
h) 4(2) cage at R6C3 = {13}
i) 13(2) cage at R6C7 = {49/58/67}, no 1,2,3
j) 12(2) cage at R7C4 = {39/48/57}, no 1,2,6
k) 6(2) cage at R7C6 = {15/24}
l) 15(5) cage at R4C2 = {12345}
m) 33(5) cage at R6C5 = {36789/45789}, no 1,2
Steps resulting from Prelims
1a. Naked pair {89} in R5C67, locked for R5
1b. Naked pair {89} in 17(2) cage at R2C3, CPE no 8,9 in R2C456 + R3C123, clean-up: no 2,3 in R1C5
1c. R3C2 = 7 -> R4C3 = 9, R2C3 = 8 -> R3C4 = 9; clean-up: no 2 in R2C5, no 2 in R3C8, no 2,4 no R4C7, no 3,4 in R7C4, no 3 in R8C3
1d. Naked pair {13} in 4(2) cage at R6C3, CPE no 1,3 in R456C2 + R79C4
1e. Naked triple {245} in R456C2, locked for C2, N4 and 15(5) cage at R4C2
1f. Naked pair {13} in R5C34, locked for R5
1g. Naked pair {13} in R56C3, locked for C3 and N4
1h. Naked triple {678} in R456C1, locked for C1
1i. R456C1 = {678} = 21 -> R37C1 = 6 = {15/24}
1j. 33(5) cage at R6C5 = {36789/45789}, CPE no 7,8,9 in R9C5
1k. 8 in R3 only in R3C789, locked for N3
2. 45 rule on N5 4 innies R46C5 + R5C46 = 22
2a. Max R4C5 + R5C4 = 7 -> min R5C6 + R6C5 = 15, no 3,4,5 in R6C5
2b. Max R5C6 + R6C5 = 17 -> min R4C5 + R5C4 = 5, max R5C4 = 3 -> min R4C5 = 2, clean-up: no 4 in R3C5
2c. R4C5 + R5C4 cannot total 6 -> R4C5 + R5C4 = 5,7 = [23/41/43] -> R4C5 = {24}, clean-up: no 2 in R2C5
3. 15(3) cage at R4C8 = {258/267/357/456} (cannot be {168/348} because 1,3,8 only in R4C8), no 1
3a. 8 of {258} must be in R4C8, 2 of {267} must be in R5C89 (R5C89 cannot be {67} which clashes with R5C1) -> no 2 in R4C8
3b. 1 in N6 only in R4C9 + R6C89, CPE no 1 in R78C9
4. 45 rule on R12 3 outies R3C367 = 1 remaining innie R2C9 + 1
4a. Min R3C367 = 7 (cannot be {123} which clashes with R3C5) -> min R2C9 = 6
4b. Max R3C367 = 10 -> no 8 in R3C7
4c. R2C9 = {679} -> R3C367 = 7,8,10 = {124/125/145/235} (cannot be {134/136} which clash with R3C5), no 6 in R3C37
4d. Killer pair 1,3 in R3C367 and R3C5, locked for R3, clean-up: no 8 in R4C7, no 5 in R7C1 (step 1i)
4e. R3C89 = {68} (hidden pair in R3), 6 locked for N3, clean-up: no 6,7 in R4C7
4f. R2C9 = {79}, R3C9 = {68} -˃ 18(3) cage at R2C9 = {189/378/567} (cannot be {369} = [963] which clashes with 11(2) cage at R3C8) -˃ R4C9 = {135}
4g. R2C9 = {79} -> R3C367 = 8,10 = {125/145/235}, 5 locked for R3, clean-up: no 1 in R7C9 (step 1i)
4h. Naked pair {24} in R37C1, locked for C1
4i. Combined cage 18(3) at R2C9 + 11(2) at R3C8 = [765]+[83]/[783]+[65]/[981]+[65] -> 5 in R4C79, locked for R4 and N6, clean-up: no 8 in R7C8
4j. Naked pair {24} in R4C25, locked for R4
4k. 15(3) cage at R4C8 (step 3) = {267} (only remaining combination), locked for N6, 2 also locked for R5, clean-up: no 6,7 in R7C8
4l. 4 in N6 only in R6C789, locked for R6
4m. 4 in N5 only in R45C5, locked for C5, clean-up: no 7 in R12C5
4n. Hidden killer pair 1,3 in R4C46 and R4C79 for R4, R4C79 contains 5 and one of 1,3 -> R4C46 must contain one of 1,3
4o. Killer pair 1,3 in R4C46 and R5C4, locked for N5
4p. Hidden killer pair 2,5 in R6C2 and R6C46 for R6, R6C2 = {25} -> R6C46 must contain one of 2,5
4q. Hidden killer pair 2,5 in R45C5 and R6C46 for N5, R6C46 contains one of 2,5 -> R45C5 must contain one of 2,5
4r. R45C5 contains 4 and one of 2,5, R4C5 = {24} -> R5C5 = {45}
4s. 4 in R45C5 -> combined half cage R34C5 + R4C5 = [145/324]
4t. Killer pair 3,5 in R12C5 and R34C5 + R4C5, locked for C5, also 3 in R23C5, locked for N2
4u. 7,9 in C5 only in R678C5, locked for 33(5) cage at R6C5, no 7 in R8C4, no 7,9 in R8C6
5. 45 rule on N1 3 remaining innies R1C23 + R3C1 = 12 = {246/345} (cannot be {129} because 1,9 only in R1C2, cannot be {156} because 1,5,6 only in R1C23), no 1,9, 4 locked for N1
5a. R1C2 = {36} -> no 6 in R1C3
5b. 6 in N1 only in R12C2, locked for C2
5c. Killer pair 2,5 in R1C23 + R3C1 and R3C3, locked for N1
5d. 5 in C1 only in R89C1, locked for N7, clean-up: no 7 in R7C4
5e. 22(4) cage at R7C3 contains 5 = {1579/3568} (cannot be {2569/2578} because 2,6,7 only in R7C3, cannot be {4567} which clashes with R8C3), no 2,4
5e. 8 of {3568} must be in R8C2 -> no 3 in R8C2
5f. Hidden killer pair 8,9 in 22(4) cage and R9C2 for N7, 22(4) cage contains one of 8,9 -> R9C2 = {89}
6. 45 rule on N3 2 innies R12C7 = 2 outies R4C79 + 1
6a. R4C79 = {15/35} = 6,8 -> R12C7 = 7,9, no 9 in R1C7
6b. 18(3) cage at R2C9 (step 4f) = {189/378/567}, R4C79 = [35/51/53] -> combined innies+outies R12C7 + R4C79 = {45}[35]/[72][35]/[34][51] (cannot be [72][53] which clashes with 18(3) cage = [783] -> R1C7 = {3457}, R2C7 = {245}, R4C9 = [15], 3 in R14C7, locked for C7, clean-up: no 5 in R3C6
[Cracked. The rest is straightforward.]
6c. R3C5 = 3 (hidden single in R3) -> R4C5 = 2, clean-up: no 8 in R1C5
6d. Naked pair {56} in R12C5, locked for C5 and N2 -> R5C5 = 4, placed for both diagonals, R9C5 = 1, clean-up: no 5 in R8C7
6e. 33(5) cage at R6C5 = {36789/45789}, R678C5 = {789} -> R8C46 = {36/45}, no 8
6f. R46C5 + R5C46 = 22 (step 2), R4C5 = 2 -> R5C46 + R6C5 = 20 -> R5C4 = 3, R5C6 + R6C5 = {89}, locked for N5, R56C3 = [13] -> R7C2 = 1
6g. R4C79 = [35] (hidden pair in R4) -> R3C8 = 8, R3C9 = 6, R2C9 = 7 (cage sum), R5C9 = 2
6h. R4C79 = [35] = 8 -> R12C7 = 9 = {45}, locked for C7 and N3, clean-up: no 4 in R3C6, no 2 in R7C6, no 9 in R7C8
6i. Naked pair {12} in R3C67, locked for R3 -> R3C1 = 4, R3C3 = 5, placed for D\
6j. R79C7 = {67} (hidden pair in C7), locked for N9
6k. Naked pair {67} in R6C6 + R7C7, locked for D\ -> R4C4 = 1, placed for D\
6l. Naked pair {39} in R1C1 + R2C2, locked for N1 and D\
6m. R8C8 + R9C9 = [28] = 10 -> R7C7 + R9C8 = 12 = [75], 7 placed for D\, R7C8 = 4 -> R6C7 = 9, R7C6 + R8C7 = [51], R7C4 = 8 -> R8C3 = 4
6n. R3C6 = 1 (hidden single in R3) -> R2C7 = 5
and the rest is naked singles, without using the diagonals.