Whole game access
This cheat only works for the American and Japanese versions.
Press Up and Start on the second joypad, then turn on the Genesis. Keep the buttons pressed until the Sega Logo comes up. Now press A and C (still holding down Up and Start) and press Start on the first joypad to begin the game.
When Simone appears on the option screen, carry on from where you left off and press A, B or C.
A will give you Chapter select
B gives you a Battle select
C will take you to the ending of the game
Note: you can’t actually save your position when you use this cheat.
Re-name all characters
This one works on all versions of Shining Force.
Start a new game and enter the name of your player. Highlight END and press the following buttons: On pad 2 hold A, B and C and press Start. At the same time, but on Pad 1, press A, C and Start together. You’ll then have another person appear on screen for you to name. The cheat will not take effect until after Lowe, Ken, Tao and Hans have joined you.
Apparently you can access a special Message Test by just holding the B button when Simone wishes you good luck. It allows you to read the game’s dialog. I’ve never gotten this one to work, but that doesn’t mean it won’t work for you!
Sound test option
Shining Force Sound Test Cheat
According to a guidebook there is a sound test cheat:
What is this screen?
This sound test screen cannot normally be seen in the game. However, we begged a normally reclusive developer who, just for us, accessed the screen for us. Unfortunately, he didn’t tell us exactly how to access the sound test. He did say that this was a special treat for those who finished the game. So, it seems that you can’t access the sound test unless you finish the game. Darn.
Many thanks to Ed for the translation!