Is there anything I am not allowed to ask for?
You are entitled to request anything in the possession of the public authority or Minister.
You only have a right to information, however, that is not exempt information, and the Act contains a number of exemptions that allow a public authority or Minister to withhold information from you if it is appropriate to do so. While the object should always be to release as much information as possible, the exemptions are there for a purpose and there are legitimate reasons why they may be relied on from time to time.
So, while there is no limit on what you can ask for, there may be limits on what you can get.
For example, you might request the personal information of any person you like, but if you have no legitimate reason to access that information, it is likely to be exempt.
Another example might arise in a commercial context. Often information is provided to an authority in confidence, or it might relate to the business affairs of a third party or even the business affairs of the authority. These are all potential bases for exempting information.