The link between InfoObjects in 2 entirely different Cubes

Hi Experts,

So I have identified all key figures and characteristics needed for a project. Found some of these in Cube 1 and Cube 2.

1.

If it is an HR project should all cubes come from HR?

2.

for a example I came across a number of VERSION TYPEs in different Cubes, can I use any of them, regardless of where I found the Cubes, as long as in business content?

3.Are the various key figures and characteristics from any 2 cubes Cube 1 and Cube 2 automatically linked together?

4.

Or, do we have to do anything like we do in databases where we need a primary need in two tables to link them?

Thanks in Advance