Unlock All Costumes, Sets and Decades in Sandbox Mode:
WARNING!! This cheat involves editing the system registry. This should only be done by those familiar with the registry as editing or deleting an incorrect item could result in system failure.

First, you must have started at least one Sandbox game. After that, use regedit or regedt32 to open the registry editor and locate the following registry value:

HKEY_CURRENT_USER ] Software ] Lionhead Studios Ltd ] TheMovies

Change the key "Allow any Decade" from a 0 to a 1.

Now, when you start a new Sandbox game you may select any decade and will have access to most (if not all) costumes and sets.

Unlock Every Reward
To unlock every reward from quest mode, go to run and type in:
C:Documents and SettingsyourusernamehereApplication DataLionhead StudiosThe Moviesunlocking.ini

Delete whatever is inside here and put in the following:

highest_decade = 2100

(prizes)
RANKPRIZE_1
RANKPRIZE_2
RANKPRIZE_3
RANKPRIZE_4
RANKPRIZE_5
RANKPRIZE_6
RANKPRIZE_7
RANKPRIZE_8
RANKPRIZE_9
RANKPRIZE_10
RANKPRIZE_11
RANKPRIZE_12
RANKPRIZE_13
RANKPRIZE_14
RANKPRIZE_15
RANKPRIZE_16
RANKPRIZE_17
RANKPRIZE_18
RANKPRIZE_19
RANKPRIZE_20
RANKPRIZE_21
RANKPRIZE_22
RANKPRIZE_23
RANKPRIZE_24

Save, and you will have all the rewards gained from story mode in Sandbox mode.

If this file does not exist, get the first reward gained from story mode to have the computer create this file for you.

OR

You could open up some type of word processer and put this in and then save it as unlocking.ini in the

C:Documents and SettingsyourusernamehereApplication DataLionhead StudiosThe Movies