It is, but for 18 move solutions and fewer, it is actually mathematically most likely that the solution is optimal, due to the rarity of the scrambles of length (solution length -1). Which explains why my 18 and Harry's 17 were both optimal. I guess Sebastiano's 18 was not, but we now have 3...
Also, the main method for solving a 4x4 involves "turning it into" a 3x3, and then solving that 3x3 with the beginners method. So he would still be able to practice his 3x3 skills!
What is your current method for recognition?
None of the above ;) You have a physically twisted corner that cannot be solved with algorithms. Solve first two blocks, phyiscally twist all of the corners upwards so that their yellow stickers are on top, and then lookup the CMLL. This should...