How can I use Sentinel for free?

Could you please elaborate on how users can utilize Sentinel's services without any cost involvement? I'm curious to know if there are any specific features or limitations that come with a free account. Is there a registration process, and if so, what information is required? Furthermore, I'm interested in understanding whether there are any trials or time constraints associated with the free plan. It would be greatly appreciated if you could clarify the benefits and drawbacks of opting for the free version of Sentinel.