If the universe is written as a 'code', then deciphering that code using the embedded keys (science?, religion?, survival?, entertainment?, you pick) means that we are in fact understanding some portion of the code. If we weren't able to have any success at all (i.e., no insights as to how to understand the universe, or find meaning in the universe, or continue surviving as a species, or finding enjoyment in our lives, etc), then you might say the code is completely non-understandable. The fact that do find success in our lives with our interaction with the universe, indicates to me that we are understanding something.
To add onto what I posted, let me say that a popular situation where a code is understood in a progressive manner (e.g., our evolution of understanding) is in games. This is usually with the intent of prolonging the 'game' for some kind of maximum effect. In fact, this is how a game can be defined. For example, Monopoly starts off with the simple rule (decryption method) to buy properties while landing on them as you and others roll dice around the board, passing 'Go' and collecting $200. The 'key' that one soon understands if you play the game is that you are better off if you buy as much property as possible, especially in terms of getting a monopoly. Soon, a second tier 'key' becomes the necessity of making trades with other players so that you establish monopolies for properties that you did not land on. Later in the game, the 'key' becomes putting houses and hotels on your property so that you can bankrupt the other players before they do so to you. The point is that at each stage in the game, you see a different level to the game, and this comes mainly from the experience of playing the game.
Monopoly has been a high selling game for a number of years because it interests the players at every level, and as you progress in each level of the game, your understanding of the nature of the game becomes more evident. Monopoly is designed to bring out our competitive natures, and for most people it is what actually happens. It doesn't take a genius to understand the basic purpose of Monopoly. The game is, in a sense, a code since it is communicating a message from the designers of the game who wish the players to understand this experience of human nature by progressively revealing it to the players as the game develops.
Another kind of 'code' that are progressive like this are movies that start off with simple circumstances, and the plot moves along by revealing more and more of the key which show how tangled the characters become. The progressive nature is not evident until things start happening at a rapid rate (e.g., plot twists), at which point people decide if the movie is good or not depending on how well the movie's characters and plots interact in this fashion.
The universe shows many signs of this kind of game/movie development. It is like it is being rolled out like a red carpet, with each new era producing an expected plot twist.
Understandable? I think so. Understood? I think not. The universe is taking us somewhere, but for what specific purpose and at what destination, I can only pray.