As for the question of whether a spirit guide is your inner self or are beings other than yourself, it isn't an easy question to answer.
If you look at it from a spiritualist type of viewpoint they are distinct persons. But looking at it from the perspective of the highest point, we are all one being, although we can express quite distinctly.
Remember that we all arose from a single celled creature and gradually differentiated - so all life forms are in that sense linked. And that is just at a physical level. So when someone says they are lonely tell them to look around and see their fellows everywhere, in the birds, spiders, snakes, the dogs and cats, and all life.
Tony