Very bright light. You should be thinking in terms of watering on an 'as needed' basis, rather than a schedule. Water when a sharpened dowel rod stuck deep into the pot comes out clean/dry. You should be able to water so that at least 10-15% of the total volume of water applied exits the drain hole. If you can't, you need to find a way so you CAN water as described, or take steps to ensure the entire soil volume gets flushed regularly. The goal here is to prevent soluble salts from accumulating and negatively affecting growth and appearance. Al

I am assuming this is the tropical, Yucca elephantipis (Spineless Yucca). Just insert the canes into slightly moist sandy soil, place in a sunny warm spot and wait a bit. Don't worry about te dying, older leaves, new shoots will soon appear. They are easy plants.

Could be under or over watering. The most common home species is really quite tropical and will start yellowing if you let it dry excessively. Paler color of new growth may be light related--get it into more sun.

I hope other more experienced growers can give some advice on what exactly to do with the plant, but there's one thing that you have to be aware of-sunburn. "so I placed the plant on my balcony 2 days ago to really give it some heavy direct sunlight throughout the day." If you just took the plant and plopped it out in direct sun with no prior acclimation I'm pretty sure a couple leaves will sunburn. If you want to put the plant outside then I would first leave it in an area that recieves ambient light from the sky with no direct sun. After a week passes, leave the plant out in brighter light for an hour, then the next day for two hours, etc. until the plant is left in direct sun for the entire day. "He said the plant could survive with no drainage... just water it once a week with 2 cups of water and provide it with lots of sunlight." Definitely untrue-I'm pretty certain that no plant can grow properly in a pot with no drainage. I might be wrong, but I'm pretty sure of this. Transferring the plant to a pot with drainage will definitely make both your life and the plant's life easier. Where approximately do you live?