Oracle 11.2 Configuring authentication
I am using the security documentation to answer your questions:


No, a minimum password life cannot be specified. Only a PASSWORD_LIFE_TIME (maximum life time) can be specified. Depending on what you want to accomplish, PASSWORD_LOCK_TIME might be what you're looking for. (Source)
Yes, this can be configured. You can expire a password, the user will then be prompted that he needs to change his password on first login. Look into the PASSWORD EXPIRE mechanism. (Source)