Licensing and end point clients

Dear Team,

I have downloaded Openfire 3.10.0.

My queries:

1. Where I can find the MAC/Android and IOS clients

2. Used the default embaded database while configuration, just need to know is there any limitations? how many users can handle the database at a time, or any specific concern

3. Is it completely opensource? or any license for the same?

4. what are the best recommendation for user's approx  400~500, configuration level

6. Is there any document for the administration guide, please share the URL

Thanks in advance.

Regards,

Manoj Majhi