3 - Why the sending is Expired?

Because the expiration date has been reached and the signatory has not signed. You must resend it if the signatory is willing to sign.  

The expiration time of a contract is defined in the settings of the template. You can check at "My templates" section at the "Expiration Time" column.

By clicking on  “Sent List” > “Expiration Date” you can check the expiration date.

Furthermore, the expired sending list can be consulted in the “Sent List”, > “Status” “Expired” (see question 2) between a time interval with date and time.