Huma, welcome to the forums
I appreciated your questions. Can I suggest you go and read the forums on the occult for the answer to your first question. That forum has plenty to say about the existance of satan and demons. the quick answer, is yes He certainly does exist. But the full story is found in that forum
And what is the meaning of life? Well I assure you if you are a hitch hikers guide to the galaxy fan like myself, it's NOT 42. The meaning of life, is to find God and to glorify and enjoy Him forever. How do I know that? Because He created you and me to have that relationship with Him, and unless we find it, we cannot find any meaning to life.
Only in relationship to God, can we answer the three questions we all like to ask ourselves at some stage in our life
1. Why am I here,
2. Where did I come from
3. Where am I going.
I hope the forums help you find the truth of that meaning.
See you in the forums
Carol