Which of the follow are correct and why? I've seen most of these constructions all over the internet but unsure the difference and if even correct at all. These are examples I chose because they're possibly something I understand and would more likely understand an answer that refers to my examples. If you don't understand or can't explain using my examples, then that's ok, just please don't refer me to other answers.
If I was him, I'd go. If I were him, I'd go. If I was he, I'd go. If I were he, I'd go. If it was sunny, I'd go. If it were sunny, I'd go. If it was my bike, I'd lock it up. If it were my bike, I'd lock it up.