by littlebro » Thu Mar 26, 2015 6:46 pm
For the garden key, yes you do need it in LF 3.
The whole thing is a bit sneaky. Because you can use it for something, and then you get another chance to get it back again so that you can use it for the particular side quest.
From paragraph #60 of my Chapter 10 walkthrough
When you get to the palace, go right, up the first set of stairs, then if you used the Garden Key when getting Luci into the Council in LFII, it will have gone from your inventory and you’ll have to do a slight detour now. You need this key – so go left through the door and along to the kitchen again, click on the second oven twice, and get it back. Return to the red carpeted area and continue going right and up until you reach the throne room.
So you can use it in LFII without any worries for the future.