Go to the library in the castle and get underground. (for more info on this, ask another question.) Then click on the switch. On the other side of the jail bars, the sewer bars go up. Then go to the field where the mill is and use the key (for more info on the key, ask another question) to open the sewer in the ground, which is between the haystacks. then go inside. walk to the left and push the dirt wall. then keep going left. go inside the small hole at the end of the dirt hallway. you are in the jail cell! click on the "invader" and it will explode.
The island that uses spacecraft to travel through the quest is Astro Knights Island.
give it to the guy in the museum and he'll let you look around
The mouse will get surprised, run around, then run back to you.
You go to Mordred's Museum and click the books on the top floor. The manager won't let you have the books, but you get the card.
Shoot at them or pass in front, but don't get chomped. You have to let them stay close to keep them following you. Move ahead, then let them catch up.
beat the beast and let the knight join your journey
No, you use him to retrieve the green fuel rod from the blown-up robot. Click Merlin then click the fuel rod.
Entering the dungeon from the castle library, you throw a switch that opens the back gate into the robot's cell. However, he can't get out that way. When you come back to the dungeon through Mordred's tunnel, the gate is open and the robot invader self-destructs as you enter. You will need Merlin the robot owl to recover the Fuel Rod. (see related question)
On Astro Knights Island when you eventually receive the rocket to explore space to find and rescue the princess, you can select, then enter, on the moon, which is filled with friendly aliens that let you customize your rocket etc.
When you have recovered a fuel rod for the saucer, the instrument will let you use the X and Y dials to set the coordinates. But the planet coordinates the Queen gave you are too far away. You will need to use the coordinates from Mordred's missing journal page, which are X-56 Y-52. (see related question)
The crossbow will let you create a way into the Princess tower. Get the rope from the water wheel at the mill and tie it to an arrow. Aim up to the left and shoot until you hit the door.
You cant. You have to let it out by the owl near morters cave.