No, it is not a Forever Stamp.
Yes. if is not cancelled. Can be used like a forever stamp.
It will say forever on the stamp. If it doesn't, it may be one of the non-denominational issues that has a fixed price. See the link below.
It is a forever stamp. It is good for the current value of a first class stamp.
A first-class stamp is not the same as a forever stamp. A forever stamp holds the value of a first-class stamp regardless of how often the rate for first-class postage has increased. A first-class stamp only holds its face value.
Yes. that is their purpose, to still be valid.
what do shake look like
Yes, you can ... forever ...
Yes, you can use a Forever stamp on a postcard, but it's overpaying for postage.
Yes, it is valid for the first ounce of First Class postage always and forever.
Exactly like any other US Stamp.
Yes