Could you explain what you mean with more detail? It obvious how to leave voicemail for an extension so I'm sure thats not what your asking. Also fowarding email to an email address is fairly simple. If you provide more detail, I'm sure the answer will be easy to provide.
Yes. It's not available from 3cx. There are two options. Hire someone to write a program and connect to the 3cx API or use Acarda. Acarda comes from a company in new Zealand and is compatible with 3cx