Whistle / Stuck in Corner

I've been making a lot of progress on my custom quest, but I've run into a snag. Whenever I blow the whistle, the little tornado comes and takes me to a screen, and I get stuck in the upper lefthand corner. I do believe it's because I didn't place the "green (spawn)" tile on the screen in which I am warping to. So I do think that I know the cause of the problem. But I'd like to ask a few questions:

1. Is there anywhere on the game where you can select the screens that the whistle warp will take you to? As we all know, in the 1st quest, the tornado usually takes you to the old Level 1, Level 2, Level 3, Level 4, Level 5, Level 6, Level 7, or Level 8. Can I reprogram these warps? Naturally, my desire would be for 8 warp screens, represented by the eight levels on my custom quest.
2. If I am able to reprogram these warps, can I prevent the whistle warp from taking Link to a screen where he has not yet obtained a triforce piece? In my quest, the whistle is obtained relatively early. So, can I be sure that when the whistle blows, Link doesn't get teleported to say, Level 8 prematurely? I don't want to give anything away!

Thanks in advance for the help!

By default, the whistle is set to use Warp Ring 8, which by default has 9 warp destinations. To change each warp destination, select which one you want to change, then select the DMap and screen and click OK or go. And yes, you can prevent the whistle warp from taking Link to a screen where he has not yet obtained the Triforce. For example, you can set warp 8 to the screen where level 8 is located, so that Link does not get taken to level 8 prematurely.

Also, if you have the 'Use Warp Return Points Only' quest rule turned on, you have to set the Warp A destination on the screen. If the rule is turned off, then you use the green Link Start position square.

Sorry it took me forever to respond to you, but thank you so much!!! I was on business travel all week, so I just had the chance to look into this now, and it's a great help!!!

oh, I still not reach this level