1. I have got upto who accessed what app and when, at what time. But didnt got a chance to see which sheet and etc..using Ops Monitor app. Not sure if current logs will record the extensive logging.
2. can be done using Section access.
here are some documents to get you started.
1. In the operations monitor, the Session Overview and Session Details sheets will show you the applications accessed. I do not think you can see the sheets accessed but you could possibly create/add a new sheet to the application to view this data.
2. I believe Section Access is what you are looking for to limit data by user. You can find plenty of information in the Community on how to implement this functionality.
Hope this helps point you in the right direction.