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Caring for mango trees, especially to get fruit, requires that they have a LOT of moisture. They need to remain moist, and humidity has to be high for them to fruit properly. Here is an article that will give you more information: https://www.gardeningknowhow.com/edible/fruits/mango/growing-mango-trees.htm

Pomegranite seeds are covered with the juicy edible portion that is characteristically rather sour. The hard seed portion will be bitter, but most people spit out that part when eating the juicy fruit portion.

Sweetness of the fruit may be related to the genetics of the variety ahd/or to the soil fertility and water management . You can't change the genetics, but you can improve soil fertility which provides nutrients for production of sugars. Use a complete organic fertilizer like this, spring and fall:
https://www.domyown.com/dr-earth-organic-all-purpose-fertilizer-p-9485.html

Adequate watering is essential to support the metabolic processes that create carbohydrates in the plant tissues and fruit. Deep water pomegranite at least twice a month during your Concord hot dry season, May-June through October. Mulch the soil surface to help retain soil moisture. Drip irrigation or light sprinkling can keep trees alive but is not enough for optimum health.

There are a number of reasons why a pomegranate may not produce fruit. This is an article that discusses potential reasons. Note that hybrid pomegranates that are grown primarily for their fancy flowers often don't set fruit. Also, the shrub will produce less as it ages. Be sure to check for tiny insects attacking during and right after flowering as these can destroy fruit during its very early stage. I hope you solve your problem this year. https://www.gardeningknowhow.com/edible/fruits/pomegranate/no-pomegranates-on-trees.htm

Did you purchase the tree, or was this planted from seed. If this is from seed, then that would explain the issue. They aren't true from seed, and will have lots of variation, including undesirable fruit.

If this was bought as an established tree, then it could be likely that it is underfertilized. This article will give you more information on the care of these: https://www.gardeningknowhow.com/edible/fruits/pomegranate/fertilizer-for-pomegranates.htm

Yes, of course. For reasons A & B, which are quite sound.

Each cultivar has its own color for the ripe fruit. Rather than looking at the color of the fruit, look at its size. Fully grown pomegranates will measure between 2 and 5 inches across. If you are still unsure if the fruit is ripe, do what the pomegranate farmers do, and tap the fruit with your finger and listen for the metallic sound of ripe pomegranates.