During furnish mode press "Ctrl+Shift" and scroll over a light. The mouse icon should change to an asterisk-like icon. Click on the light to bring up detailed light options "Turn off light", "Set Intensity", "Change color".
Command window
Click Control+Shift+C to make the cheat window show up, also you can type help for cheats.
How to not die
All you need to do is save your Sim when you created him or her and then when you saved your Sim in create a Sim, when you die all the things in your inventory will still be there and your characters will be alive again so you can die and die as many times as you want But you lose your husband or wife or boyfriend or girlfriend.
Partial Floor Pattern
During Furnish mode select the desired floor pattern from the available floor patterns. Press and hold "Shift" while hovering over the active floor Left-click the mouse to place the partial floor pattern. This allows the user to place floor patterns in partial sections rather than whole grid squares.
Testing Cheats mode
Use a text editor such as notepad to edit the "Commands.ini" file in the "\Program Files\Electronic Arts\The Sims Medieval\GameData\Shared\NonPackaged\Ini" directory after turning off its "Read Only" attribute. Change TestingCheatsEnabled=0 line to TestingCheatsEnabled=1 and save the file. Start the game and you will be able to click and drag the Hunger, Energy, and Relationship bars to the left or right to adjust their values. Additionally, you can type help at the console window to show additional cheats that are now available.
Various Cheats
Press Ctrl+Shift+C to bring up the command prompt anytime during gameplay or furnish mode with few exceptions.