Making contracts public is as simple as marking any contract whether pre-existing or being created as such. This won't stop you from being able to still make changes and instead will still allow the manipulation of your contract in full.

Access to the public contract is very easy, the individual trying to access the contract simply needs to go to the web address of the application themselves and navigate to the public contracts section. The information present is view only, so no need to worry about any malicious parties altering your data. The information that the public can see can also be altered with its own custom rules like every other user in the system.