What are the chances of getting into a PHD program even if your graduate research is completely different? I have decided to apply for PhD in cybersecurity even though my research during my graduate time period is totally of a different topic, which is neuroscience. My CV is majorly focused on research in neuroscience and data science and it doesn't contain any previous experience even though I have been learning a lot in cybersecurity and getting trained in the area.

What are my chances of getting into the program(in US, Sweden, UK) even thought I don't have a research experience in Cyber security nor have worked on a project?
Completely possible!

You only need to argument your research as multi-field with an holistic approach, base your methods or the relation on technology and how it impacts the new field, or propose some innovative way to apply or relate computational sciences to biological systems (neural networks or Ai to learn how X works are always a good hit.)

As as example, my first career was in 'environmental improvement and diagnostics', then I went into 'informatique sciences' , specialization MBA into 'economy', then MBA into ' Computational Systems' but PHD in 'Organizations direction/Management'. It all comes down on how you relate everything.

As for how easy it would be to enter, well, you need to see which universities you want, go into their website's  and see their requirements for candidates. You can then tailor your proposal to them and contact the admissions department to say what they want. Even within the same country there are variants among the universities, more so between public and private ones.