Forever
As of 2016, one standard forever stamp costs 49 cents.
It is a forever stamp. It is good for the current value of a first class stamp.
An unused Forever Stamp is worth whatever the current postage rate is. At the moment that's 49 cents.
Yes
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, you can ... forever ...
Forever stamps will have the word FOREVER printed on them. If the do not have a value and do not say forever, they have a fixed value.
No, only one Forever stamp has been issued. It has a value of 44 cents currently. There is a listing of USPS postage stamps that have been issued without values on their website.
The Liberty Bell is pictured on the Forever Stamp. They are worth the current value of a first class stamp, which is 44 cents in 2009. They can only be used for US addresses.
No you cannot use them. Forever stamps can only be used for domestic (inside the US) mail. They must have a value on them for international mail.
No, it is not a Forever Stamp.