1) What is the medium in which to keep the Hyacinth bulb with the long roots? 2) Do I use potting soil in a pot and the cover it as suggested above?
Sometimes, they can have trouble transplanting into soil, but this will be the only way to keep it alive passed flowering. This article will help: https://www.gardeningknowhow.com/ornamental/bulbs/hyacinth/hyacinth-bulbs-in-pots.htm
Last year I purchased a hyacinth that was in water; I noticed just the other day that the roots had detached from the bulb, is this normal? Should I plant in soil or can I keep it in the vase with water?
The roots detaching is not good. It is a sign that the water was stagnant for too long. I recommend changing this every other day, or even better, daily. You can try and let it go dormant and store it but It might already be infected.
This article will help you in storing these: https://www.gardeningknowhow.com/ornamental/bulbs/hyacinth/curing-hyacinth-bulbs.htm
I have my hyacinths outdoors in the ground. They bloomed really pretty the first two years, and now they some plants only has one little tiny bloom. Some don't bloom at all. Is there anything I can do to make them bloom?
It could be that the soil is lacking phosphorus or potassium, or the pH is off, which can lead to the same symptoms.
I would advise adding dolomitic lime to the soil to help the pH, as well as potassium phosphate. If you cannot get this where you are, or online then fertilizers that are high in potassium and phosphorus will be fine.
I purchased a hyacinth bulb in a glass vase with water on January 27 at my grocery store. It grew a beautiful flower. I've recently cut the flower bloom off since it was faded and browned. All I have now is the green leaves along with two daughter shoots. It's still growing very well in the same vase with water. This plant was forced into blooming as if it was spring time. The roots are still intact and healthy. I'd like to keep this plant for a long time growing in it's own pot with possible soil. Please advise me on how to do this.
You can easily plant these in soil. Start with moist soil, and place the bulbs in until they are about 3 to 5 inches from the top. Cover with more moist soil to the top. This article will give you more information for their care from here: https://www.gardeningknowhow.com/ornamental/bulbs/hyacinth/care-for-hyacinth-houseplants.htm
Can a hyacinth indoor plant be planted outdoors after blooming?
First you will want them to enter dormancy, then store for a couple of months. Then you can plant them. This article will help you in properly helping through dormancy: https://www.gardeningknowhow.com/ornamental/bulbs/hyacinth/curing-hyacinth-bulbs.htm
This article will help you on their care when you plant: https://www.gardeningknowhow.com/ornamental/bulbs/hyacinth/planting-and-care-of-hyacinths.htm
d then cut them off? And what do I do with the potted bulbs? Do I continue to water them before planting in the ground this spri ng?
Yes, you will want to wait until the growth is almost completely dead before cutting off. After this, you will not want to water them until they have gone through a dormancy period of a month or two. This article will give you more information: https://www.gardeningknowhow.com/ornamental/bulbs/hyacinth/curing-hyacinth-bulbs.htm
How do I care for hyacinth plant?
This article will give you information on growing these: https://www.gardeningknowhow.com/ornamental/bulbs/hyacinth/planting-and-care-of-hyacinths.htm