you can also use the history option in the Team tab to see commits.
There is no approval process for doing this. It would have to be something that you set up internally with your development team. In order to manage merges that were "unapproved", which would be someone merging a branch to mainline and committing, you can use the "Reverse Merge Changes" in the team tab to revert someone elses commit.
Here is some documentation on this. Specifically in the "Reverting Changes" section