yes, any fabric that is called cotton is usually 100% cotton. However, calico refers to the design, not the fabric content, and could be made from any type of fiber.
Combed cotton is softer and finer than ordinary cotton. Impurities in combed cotton were brushed out after the initial spinning.
Yes, often times it is, but you need to check the label. Sometimes it's a cotton polyester blend.
The most shrinkage is by hot water washing and machine drying at higher heat settings.
JEANS