Sake is primarily made of rice and water

The alcohol content of sake is generally 15-17%

Sake can be served both gently warmed or chilled. It really depends on the type. If you have an elegant Daiginjo, warming may dull any subtle aromas and complexities. However, a hearty Junmai may open up when warmed.

I would suggest that you drink it using a wine glass. This would allow you to see the color and clarity of the sake and allows the sake to express its aromas and flavors as compared to drinking it in a cup.

Ideally, it would be best to consume the sake as quickly as possible after opening it. If it is kept sealed and in the refrigerator,  it can be consumed for several weeks, however, the flavors will soften considerably.

I recommend that you store your sake in the refrigerator. This keeps the sake away from light and heat. This goes for pasteurized or unpasteurized sake.

Yes. There are about 65 rice varieties used for brewing sake. Like grapes, different varieties grow best in certain regions. Some examples of rice varieties used for sake are Yamadanishiki, Gohyakumangoku, Miyamanishiki and Omachi to name a few.

Its color or shade darkens. This happens at a faster pace when exposed to light and heat. 

A 120 ml serving of sake would have about 120 calories

It is safe to say that a sake is gluten-free whenever it has the word JUNMAI in its label, meaning it is of that category which is made of only pure rice alcohol.

Sake would be a friendlier choice as compared with other alcoholic beverages. Sake has much lower levels of acidity (about 1/3 of wine) and is very clean. It does not contain any preservatives such as sulfites. Sake is a naturally fermented alcohol beverage made from rice and water.