Junior Eligibility

The CFL draft is just a few months away and I was wondering about eligibility and how it all works so I thought I'd ask the smartest people I know with respect to all things CFL, you.

Let's start with Junior Football:
How does Junior football, Teams like Nanaimo, Saskatoon, Winnipeg Rifles, etc. fit in. I do not recall players from here ever being drafted. I do recall players like Andrew Harris, Rollie Lumbada, Zach Evans, Stu Foord and a few others who played junior earning spots on CFL clubs but how do they get to CFL camps if not drafted.

I think I have heard as well that CFL clubs can carry a junior player on their practice roster without counting him or affect the junior player's eligibility to play junior or move on to University later. Can anyone confirm that this is true or not or clarify that for me?

Can a university player be on a CFL practice roster while still playing University football?

Thanks for any answers you can give.