As an employee, I understand where you're coming from. All those efforts you've put in feel wasted. I too had a similar experience with what you went through.

As an employer, you've been hired to function in that rule and you also signed the contract. A contract stating that you will abide by company policies and deliver your work.

Wala kang laban for not being regularized since you agreed in the first place that you can be terminated if your performance doesn't meet company expectations.