1. Do Data Guard and Golden Gate offers same features ?
==)> The main difference between them is that Golden Gate can work across different versions and in fact across different O/S platform.
2. Which products offers solutions to all my requirements or Do I need to use both ?
==)> Both works. However, if you have same platform/db version, Active Data Guard is better option, as this can also server you as pure DR site.
3. If Data Guard and Golden Gate are different from each other then What is the difference between them and what are the overlapping features among them ?
==)> Difference is mentioned in #1 above and main overlapping feature is that both are 'replication' solutions.