R1C3 can only be <7>

R4C2 can only be <6>

R5C5 can only be <6>

R7C9 can only be <1>

R9C3 can only be <8>

R4C8 can only be <7>

R4C1 can only be <8>

R5C3 can only be <1>

R7C1 can only be <9>

R4C9 can only be <5>

R7C5 can only be <8>

R1C4 is the only square in row 1 that can be <8>

R5C1 is the only square in row 5 that can be <7>

R5C9 is the only square in row 5 that can be <8>

R6C8 is the only square in row 6 that can be <6>

R6C2 is the only square in row 6 that can be <9>

R5C2 can only be <3>

R5C8 can only be <2>

R6C1 can only be <2>

R5C7 can only be <9>

R9C8 can only be <3>

R6C9 can only be <3>

R3C9 can only be <4>

R8C9 can only be <7>

R9C7 can only be <2>

R1C8 can only be <1>

R2C9 can only be <2>

R1C7 can only be <3>

R1C6 is the only square in row 1 that can be <2>

R9C5 is the only square in row 9 that can be <9>

Intersection of column 4 with block 8. The value <5> only appears in one or more of squares R7C4, R8C4 and R9C4 of column 4. These squares are the ones that intersect with block 8. Thus, the other (non-intersecting) squares of block 8 cannot contain this value.

R8C5 - removing <5> from <1345> leaving <134>

Squares R1C5 and R8C1 form a remote locked pair. <45> can be removed from any square that is common to their groups.

R8C5 - removing <4> from <134> leaving <13>

Intersection of column 5 with block 2. The values <45> only appears in one or more of squares R1C5, R2C5 and R3C5 of column 5. These squares are the ones that intersect with block 2. Thus, the other (non-intersecting) squares of block 2 cannot contain these values.

R2C6 - removing <4> from <147> leaving <17>

The puzzle can be reduced to a Bivalue Universal Grave (BUG) pattern, by making this reduction:

R2C5=<14>

These are called the BUG possibilities. In a BUG pattern, in each row, column and block, each unsolved possibility appears exactly twice. Such a pattern either has 0 or 2 solutions, so it cannot be part of a valid Sudoku

When a puzzle contains a BUG, and only one square in the puzzle has more than 2 possibilities, the only way to kill the BUG is to remove both of the BUG possibilities from the square, thus solving it

R2C5 - removing <14> from <134> leaving <3>

R2C1 can only be <4>

R2C4 can only be <7>

R3C5 can only be <5>

R8C5 can only be <1>

R3C1 can only be <3>

R1C5 can only be <4>

R8C6 can only be <4>

R8C1 can only be <5>

R9C6 can only be <7>

R9C4 can only be <5>

R2C6 can only be <1>

R1C2 can only be <5>

R8C4 can only be <3>

R9C2 can only be <4>