[havemylife]

I'm by no means well informed on these topics, but I'm unsure where you're getting your 2 billion year estimate. Furthermore I thought that Earths magnetic field shielded from solar radiation, and additionally that there's a significant amount of radiation in space anyways.

Further questioning I have though is, does solar radiation penetrate through ocean water?

What radiation is between solar systems or what rogue planets would likely encounter, and how that effects single cell life, amino acids, organic compounds, and any other building blocks to life?

[gambiting]

>>Further questioning I have though is, does solar radiation penetrate through ocean water?

Barely. 10km of water will shield you from almost any amount of radiation, and we know of life forms which live at those depths, so they could have developed even when Earth was completely bathed in radiation.