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You may either be overwatering or there may be an issue with the roots. Water only if the soil is dry to the touch. If you are already doing this, check the roots for root rot. This article will help with that:
https://www.gardeningknowhow.com/plant-problems/disease/treating-root-rot-gardening-tips-for-housplants.htm

Yellowing of the bottom (older leaves) is generally ok provided that the remainder of the plant is thriving. Simply keep doing as you are and remove the old, yellowing foliage (carefully, these may still be sharp). Occasionally, this can be attributed to an over abundance of moisture or even a nutrient deficiency, but typically these plants rarely become affected by anything too serious. Water the plant only when the soil is dry to the touch.

To kill it, cut it down as close to the ground as possible and then paint the fresh cut with concentrated Round-up. Keep an eye on it and if you see any shoots, you can repeat this process. This article will also help: https://www.gardeningknowhow.com/ornamental/foliage/yucca/removing-yucca.htm

Yuccas are fickle when it comes to blooming. They need to be mature enough first, which takes 3-5 years. After that, it is a matter of how well they have stored energy. You can try to give it some bone meal to help it with storing the energy needed for blooming, but with yuccas it is ultimatly a wait and see for blooming.

Yes, it will bloom again. Yuccas do not always bloom every year, so it may be skipping a year. It is fine to leave the growths. They will not harm the plant. Yes, you can remove the dead leaves. There is no reason for them to stay on the plant.

Yes, and these article will help: https://www.gardeningknowhow.com/ornamental/foliage/yucca/yucca-plants-care-and-pruning-tips-for-pruning-a-yucca.htm
https://www.gardeningknowhow.com/ornamental/foliage/yucca/yucca-cold-weather.htm