The solutions to the 3 puzzles given your program are as follows:

Number expanded 29. Sol. Length 13
(INITIAL U L D L U U R D R D L U)

Number expanded 1.  Initial is goal node.

Number expanded 233. Sol. Length 21
(INITIAL R U L L D D R U U L D D R R U U L L D R)


Note: I am counting trying to expand the goal node as an expansion.  You
did not have to do this to get the correct answer.  It is possible that you
make different choices in cases of ties than I do, leading to a different
number of expanded nodes for puzzle 3.
Puzzle1

(8 1 3  7 6 4 5 2 b)

Puzzle2

(1 2 3 8 b 4 7 6 5)

Puzzle3

(8 4 5 3 b 7 2 1 6)