Welcome, Kevin. Thanks for all your questions. Your first one is perhaps best answered by an article on the site called "Do People Who Don't Believe in Jesus Go To Hell?". Please let me know if that helps to answer your question about people who don't believe in Jesus.
Has anyone seen God? Yes, some have, depending on what you mean. It's fair to say that Jesus was God, and thousands of people saw Him on earth during His ministry. Some people have seen what I would call "manifestations" of God the Father such as the burning bush or the pillars in the desert. But no mortal can actually see all of God, since He does not have a physical body in the same way that we do. But God can make images or parts of Himself visible to people, and has done so in the past.
I'm not sure why so many people worship idols, but I think it's because they lack faith and so they need something they can see. I suppose they would rather worship a fake god they can see and touch rather than the real God who is invisible. There are other idols, too. Some people worship money or power. Anything that gets between us and God, or takes the place of God in our lives could be considered an idol. I guess the simplest answer is that people worship idols because we are fallen and prone to sin.
I'm not sure what to say about meditation. I would not say our mind goes to God, but meditation does open our mind and make it easier to focus. Sometimes it's hard to really focus on God and prayer, so mediation makes it possible to get away from the distractions, silence our mind and really spend quality time with God.
These are all excellent questions, and I've only scratched the surface, so please feel free to let me know if there are any areas where you would like me to elaborate. I'd be happy to answer any other questions you have, or explore these subjects with you more deeply.