as far as i've been told, spirit guides are chosen because they are a higher being than "normal" spirits, if that makes sense? They are chosen to help us with our lives, so i dont think they could just be "normal" spirits, if that makes sense? I will ask DP more about this, as his mum has spoken to her spirit guide about tis before... and then i will answer your questions

Feel free to ask any questions! I love being able to speak to people about this stuff!