1. The solver stops at the following position:
A36 must be [1234] eliminating 89 from the compartment.
The highest number in A3 is 4 so the highest in AD3 is 7 eliminating 89 from the
compartment.
The solver then progresses to the following position:
Each of AC4 and AC5 must contain 34 eliminating those numbers from the rest of
columns 4 and 5 along with the stranded 2 in GJ5.
The lowest number in J4 and J5 is 5, eliminating the 1 from J6 and J7.
D13 must be [234], [345] or [456] and must contain a 4, eliminating that number and
the stranded 23s in D69.
D7 is higher than 5, so everything lower than 5 is eliminated from BD7, and
everything higher than 5 from FJ7.
The solver stops at the following position:

2. GJ5 must contain 67 so those numbers can be eliminated from E5.
The lowest number in F3 and F4 is 5 eliminating 2 from F14. F14 must be [3456],
[4567] or [5678] and must contain 56 which can be eliminated from F79. F79 must
contain a 3 which can be eliminated from F14. The highest number in F9 is 4,
eliminating 9 from EH9.
J4 and J5 are each [56] so J6=3 and J7=4.
F7 cannot be 3 or GH67 would be an impossible pattern as the puzzle has a unique
solution (see notes on Unique Rectangles in the Sudoku solver).
D6 and D8 are each [56] so D69 must contain a 5, eliminating 9 from D7.
DH7 must be [12345] or [23456], and must contain 2345, eliminating those numbers
from B7.
Each of C3, C4 and C5 is [234], so C17 must contain a 2 and therefore cannot
contain a 9.
B4C5 is an x-wing on 4, eliminating the other 4s in rows B and C and thus solving D3
for 4.
The 4 in D3 reduces D1 and D2 to [23], and the maximum in the column 2 and
column 3 compartments is thus 7.
B4J5 is an x-wing on 5, eliminating the other 5s in columns 4 and 5.
E1F2 is an x-wing on 4, eliminating the other 4s in rows E and F, thus solving F9 for
3 and eliminating the other 3s in row F and column 9.
The solver then stops at the following position:

3. As BF1 and BF2 both contain a 4, F14 must contain a 4 and therefore cannot contain
an 8, thereby solving F4 for 6, H4 for 8 and J4 for 9.
The solver does the rest.