Elgg for Android Development

Hello everybody....I am new to Elgg. and also new to this group as well. We are working on a Social Networking app on Android Platform. And for this purpose we have to do the following tasks.

1.User can create their accounts

2. Giving different privileges to different kind of users

3. User can create a group and they can add other members in this group

4. Storing map locations of the users on back-end database

5. User can message each other and they can post something on their wall

6. a User (Manager) can assign a list of task to other members of the group (sub-employees)

Now the question is that can we do these all mentioned tasks by using elgg on back-end. If YES. then
1. How we'll connect android app with elgg

2. How the DB will work and

3. How we will parse the data from DB and what will be the role of Elgg. there....

Any kind of suggestion will be helpful for us...Thanks in Advance.

Hope for a Positive response from the community