What's your question? Ask

It is a variegated yucca. This is normal during wet seasons. There are many fungal infections that can affect this small shrub, and most will go away on their own. You can help this along faster by applying wettable sulfur and dolomitic lime.

These are quite drought tolerant. I would only give it water when the top two inches of soil are completely dry. This will vary since the conditions around it will affect the time it takes to dry out.

As for how much to use when you water... I would make sure that your container has good drainage and that extra water is allowed to leave the container. Sitting in water will certainly lead to infection. If there is no drain hole/s then I would recommend changing pots. Leave a drip pan under it so that you can throw out any extra water that sits after watering. The amount that you water will have to be learned over time. Eventually you will get to where you won't need a drain pan, or holes, as you will know exactly how much water a particular soil is capable of holding.

They don't seem to be sensitive to tap water, so this is fine to use, but rainwater is always a safe bet.

This article will give you more information on the care of yucca: https://www.gardeningknowhow.com/ornamental/foliage/yucca/growing-yucca-indoors.htm

This article will help you: https://www.gardeningknowhow.com/ornamental/foliage/yucca/yucca-seed-pods.htm

This could be due to water contain too much salt.
This article will help you.

https://www.gardeningknowhow.com/ornamental/foliage/yucca/yucca-turning-brown.htm

Most cuts or wounds will heal on their own and covering them is not recommended.

Those will be flower heads! They will turn into seeds and spread. These will be hard to control, as they spread from underground tubers. The only way to get rid of these without harming the roses will be to remove them by hand each time you see one come up. It will take a few years, more than likely. Once these get established, they will take over an area very quickly.