AIXI is an artificial 'general' intelligence. It is not hard coded to do a specific task. That neural network is useless at doing anything other than playing tic tac toe
Actually no -- it's the neural network + biases, start values that's good at playing tic tac toe. The neural network code itself is not "hard coded" for any specific task.
You could use the same neural network with different inputs to do other stuff, like recognize characters, and all kind of pattern matching / classification.