Unfortunately, this is not possible as the Google bots index your website as a guest user, you can arrange so that bots could join your website in the web master tools, but we use AJAX sing up form and it might cause troubles for them to join. Which is why, we recommend you to change the setting for guests as "Yes"

But is there another way to restrict guest's activity on my site without afecting google's bots? Just my socia network is klosed one and I don't wanna other unsigned people to vew the content, and at the same time I need this site to be indexed by google. Please, advise me a good solution to solve this issue. Thanks in advance.

As I said Google bot is equal to your your gust member. I don't follow the reason to have a closed and indexed by google website. However, you can make unvisible the links and widget for the guest member and configure via web master tools so that a google bot could join your website. 

Sorry for this stupid question, but could you tell me how I can configure via web master tools so that a google bot could join my website. I'll be very tankful for your help. Thanks in advance!

Please, read this article: http://support.google.com/webmasters/bin/answer.py?hl=en&answer=182072

And what whould I do? I've read but I have no idea what and where to add to make my iste indexed by google bots. Please give a step by step instruction what should I manage?!

This is all I can do for you. Please, google it by yourself as we do not provide such service

So, you said that I should ''configure via web master tools so that a
google bot could join your website.'' thats why I'd like to know where and what I should add to do it. I don't need any services to be provided to me, just give me a hint the direcrion I should look for because this CMS if I understand right, has some specifics that won't allow me just to add the site in web. M. tools?!

I even don't understand what to search in Google, please advise me how to do it, I really need it very much. Maybe anyone else met and solved this problem? share your expeeience please!

In this case we do not provide with specific instructions, this is general questions section of the forum

Where I have to ask for help to my problem?

As I said earlier google it. 

What to google for? I don't understand how to alow google bot to acces my closed type oxwall website. Maybe I don't understand something but I've been serching for a while without knowing what to look for. On the google I found only how to deal with ajas sites but didn't find anything about how to make google bot to login as user on my oxwall site. Thats why I ask you ''What I have to do to allow google bot to acces my wwbsite and scan all pages for their further indixation? ''. I really don't know how to solve this issue and ask you as an expert. If you know, is it so hard to give me a good advice how to do it?! Or move my question in another section where anyone else will be able to help me.

This is custom code modification and we do not provide such services, you can do such by yourself if you're good at PHP, CSS, HTML and Javascript or find a developer for that end.