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Yes, callas make good indoor plants, especially if they spend summers outside. Here is some info on growing and caring for calla lily plants that should help, if you have not yet seen it: https://www.gardeningknowhow.com/ornamental/bulbs/calla-lily/growing-calla-lilies-and-care-of-calla-lilies.htm

They normally go into dormancy in the winter, but ones that are in containers can be forced into dormancy anytime. They may need more water and light to avoid going into dormancy, or you can just let them go and then enjoy another round of blooms indoors later in the year. These articles will help: https://www.gardeningknowhow.com/ornamental/bulbs/calla-lily/make-calla-lily-bloom.htm
https://www.gardeningknowhow.com/ornamental/bulbs/calla-lily/growing-calla-lilies-and-care-of-calla-lilies.htm

Calla lilies' flowers normally start out green and will gain color as the flower ages. This is normal. As for the buds not opening fully, in addtion to keeping it watered, you can also add some phosphorus, such as bone meal, to the soil.

Simply divide the rhizomes in the spring or fall and replant/repot.

There's no need to worry about the green color. On some types this is the normal progression for calla lilies. These flowers do that as they mature and begin producing seeds. You can cut them off or leave them be.

Other possibilities include poor pollination, which can result in green color and too much light can turn the spathes green.

If you're not saving seeds, you can simply cut it off or leave it. You can also choose to save the seeds by cutting off the dried seedpod and storing the seeds in an airtight container until ready to plant. Of course, seed grown plants will take longer to produce flowers. Here is an article that you may find helpful: https://www.gardeningknowhow.com/ornamental/bulbs/calla-lily/growing-calla-lilies-and-care-of-calla-lilies.htm