Guards
It was previously revealed that the guards who patrol the stages can capture the boy you control, and if they carry him to a certain area, the game will end. However, even if captured by the guards, its possible for the boy to escape. There's a risk in doing this, said Ueda, although he wouldn't share details. Because of this, the basic play style involves trying to avoid being spotted.
Character Growth
It looks like the boy will grow through the course of the game. I'm not sure if Ueda is speaking about getting stronger in a gameplay sense, or if he means the boy will mature as part of the story. Regardless, the character will not grow in such a way that he'll be able to defeat the guards.
Torico's Interests
The press demo showed Torico appearing to be more interested in things like barrels and jars rather than the boy. Torico will move to the things that interest him most. He won't just interact with the boy because he's there. However, if you improve your communication with Torico, his interest in the boy will grow, and he may end up placing greater focus on the boy.
One example of the growing relationship can be seen when Torico is asleep. If the boy attempts to awaken Torico by by pulling on his ears, Torico won't rise. This is because he's uninterested in the boy. However, if their relationship grows, you'll be able to use this technique to wake Torico up.
Details
As Ueda has indicated in other interviews, they're putting a lot of effort into the various motions of Torico. You'll see different reactions from Torico depending on which ear you touch. You can make Torico sneeze by touching his nose. And so forth.
Riding Torico
Torico has the ability to run. He'll run, of his own accord, if he's in a wide and safe space.
I believe this was in response to a question about being able to ride Torico. Ueda didn't really say if you can ride him or not -- just that Torico can run.
Torico's Enemies
Torico considers the guards that patrol the stages to be his enemies. He'll strike them even if you don't give him any orders.
Actually, you won't really be able to order Torico at all at first. Even if you guide him to open a door by flipping a switch, you won't actually be ordering him to flip the switch, but getting him to play around with the switch. However, as your relationship deepens, you will be able to direct him, to a certain extent.
Stages
The stage that was demoed for the press showed the basic progression system for the game. You'll find yourself in an enclosed area, and to advance, you'll need to break through -- for example, opening a door that blocks your path.
What's beyond the doors? Ueda wouldn't get into specifics, but did say that you may find the outside world expanding out before you. These areas could see form changes as a result of Torico moving through them.
Although we've only seen a small number of areas, Ueda assured that the final version of the game will have great variety of stages. There are narrower stages that the the one shown in the demo, and wider stages too. While the demo stage focused on puzzles, you'll also find more action-oriented stages.
Those more expansive stages may have giant enemies. Ueda wouldn't say for sure.
If you happen to find yourself in a stage with a massive drop, watch out! If the boy falls from a great height, he'll die. You can fall to a certain extent, but not from super high up.
The game won't have a portal-like location which you set out from then return to. You may actually not be able to return to some locations because of stage form changes due to Torico.