1. If my site members crossed with 1000 or 10000 or more what security deployment has to be made?
That's up to you. Your website, your choices of what security methods you take. As of now, Oxwall has a lot of built-in security tools. They make it hard for people to crack into accounts, perform XML attacks, and to stop HTML/SQL Injections. So, no worries there. More members don't me security fails, it just means you might be more of a target for hackers. With plugins like "Brute Force Protector" and other security measures in the store, you should be fine.
2. How much hosting space and bandwith will be required for this? I have all the option on for my website like newsfeed, comments, photos videos and others.
With no members, on a fresh install you should only need about 512 MB in bandwidth. But as more users and content generate and more requests are made onto your server, you will need to expand.
3. All the plugins are working till long time? Recently i have used facebook connect plugin but it seems to be crashed or having bug in that.
Plugins are meant to work, otherwise they wouldn't be allowed on the store. This doesn't mean other plugins will collide with another or one plugin can run into a bug however. Just stay in touch with developers and you'll be fine.
4. In my website the users are not online but it appears as online its a bug?
Problem with your CRON setup. Make sure your CRON jobs are set to run for every second, minute, hour, day, and month. You can also try loading yoursite.com/ow_cron/run.php
~Jake
www.ewtnet.us
