MonoX blog system is not oriented to social networking friends and groups (although you can extend it by your self with a bit of programming).
Can be viewed only by my friends or a particular group
My suggestion would be to add the BlogContainer
WebPart to some page and then manipulate the visibility of BlogContainer
directly on the page. To do so you can use the following built-in repositories and BLLs:
With these few classes you can get all the Group statuses and Friend relations for your scenario.
Only my friends or a particualr group be able to comment
For this functionality you will need to inherit the BlogContainer
WebPart where you will do almost the same but this time for comments permissions
I hope that I have pointed you in the right direction, let me know if you need anything else.