No they will not buy back stamps
No.
No, you can not resell your stamps back to the post office.
Sure, why not? You already payed for them.
Stamps in the US can always be used at face value. The post office won't buy them back, they will tell you to use them.
Yes, you can still use old unused stamps to mail letters even if they are several years old. The post office will not reject the letter as long as the postage value on the stamps matches the current rate for mailing. However, if the postage amount is not enough, the post office may return the letter to you for additional postage.
Yes, they will exchange damaged stamps for similar stamps. They will not give you back you money.
Mauritius 'Post Office' stamps was created in 1847.
If you are a philatelist, you can purchase stamps from all over the world on eBay. There is also an official website for the Indian Post Office called e Post Office, and there you can purchase stamps online.
The post office does not pay the estate.
Yesterday I went to the post office to get some stamps.
Yes, they have some value to collectors. Those issued by the US Post Office cover a wide spectrum of values and worth. Consult a postage stamp catalog of US Stamps and look to the 'Back of the Book' for postal stationary.
send them in
One can find reliable information about different kinds of post office stamps by visiting a local post office where one will all sorts of stamps and other items like envelops.