Not-forgetting is a must for both prizes now, but I think its definition is not exactly given.
The third item of Evaluation Criteria in p. 6 of "General AI Challenge: Specifications of the First (Warm-Up) Round: Gradual Learning - Learning Like a Human" states
"For example, after solving tasks 1, 2, 3 and then 4, agent must still be able to solve tasks 1, 2, 3 (with the same or better performance)".
Literally, this only means "The agent must be able to re-learn 1, 2, and 3 after learning 4, and the speed must not deteriorate." I think this is a very weak, unimportant restriction, not exactly corresponding to the meaning of "forgetting", but at first I thought this was what the organizers have in mind, because the agent MUST forget last task and last task instance in order to solve micro-tasks A.2.1-A.2.5.18.
However, in micro-tasks A.2.6-A.2.20, each input is prefixed with a "command" word which is redundant when solving each task independently, and it is quite natural and meaningful to require that the agent can solve, say, task A.2.6, A.2.7, and A.2.8 WITHOUT LEARNING after learning A.2.6, A.2.7, A.2.8, and A.2.9 in this order. In order to do this, the agent must "understand commands", i.e. learn the map from commands in strings to functions resulting from interpreting the commands.
So, which do you mean by forgetting?