[support] group permissions

Hi, I'm trying to setup drupal 7 as intranet for my labolatory but found some poblems I can't solve.

in my institude there are couple groups which should have corresponding groups in drupal. members on ex. dba group: 1. should be able to create pages visible only to member of this group. 2. should also be able to create pages visible to all but without possibility to edit. 3. should be able to create pages visible to members of ex. three groups where one group has only read access remaining grour have write access.

I have tried to use for it organic groups but I can only do point 1. 2. all users are able to edit. 3. can't see any option to do it.

is in drupal any option to do point 2 and 3. thanks Woj