a couple of thoughts:
>If not, Can an application require registration to use? If registration is done, is there a way to allow use for 30 days, then require registration to continue?
Required registration is a good way to kill your app before it gets started. A 30 day trial will probably not do much better considering the high abandonment rate of most apps in the first few days of use.
Some apps encourage you to register/sign up so that you can benefit from future communications and updates. But they don’t require you to register.