Connecting Closed And Open Paths

I have created a Closed path(circle) using the Eclipse tool and i used scisscors tool to cut through it then i draw a straight line using the pen tool, So basically i have 3 paths.

1 - the first part of the eclipse path

2 - the second part of the eclipse path

3 - a straight line made using the pen tool

Q1- Now as the eclipse path(the circle) was firstly as a closed path now as i cut throught it and made it two separate paths, are they now converted to Open paths?

Q2 - I can still join the separated parts of the eclipse using Ctlr+j but i cannot join the line(made with pen tool) with any part of the eclipse(circle paths), Why?  

UPDATE : after experimenting almost a day(yeah a full day) i figured that when you create a line with pen tool you have to select any anchor point of that line and click on the "cut path at selected anchor point" (a curved line having scissor under it) then you will be able to join the path(created with pen tool) with any other path (created with eclipse tool but have end points ).