Realize it was God's will for Lucifer to be the most handsome and talented angel. It was God's will for mankind to live in a world that was nothing but good.
If God is All powerful why doesn't He stop it?
If God is loving why does He allow some to perish?
If God is all knowing why doesn't He stop things before hand?
The argument as you already know is call
freewill. God wants you to be saved, why aren't you? People pray for you to be saved, why aren't you? Because you don't want to right, you don't believe in Him. If God is all-loving He isn't going to make you want Him, by forcing you because He's all-powerful. He knows what will save you, but doesn't again want to force you.
Same answer to everything.
Like I said the problem is putting it all on God when it's us. Lucifer wanted to be higher than God, mankind wanted to be their own God. God allows us to fully exercise our freewill because it allows mankind to be able to search, and understand the things of life, as well as live in harmony with God. Yet because of freewill one equally has no pressure to live with God either.
This also effects prayer. I've heard from eye witness people who got healed in various ways, one being deafness another blindness, and after being healed, guess what? They prayed to be deaf and blind again. It was God's will for them to hear and see, but their will got in the way.
The Muslim argument would be what as you started this post with, that God is mysterious, we can't always know His ways. Remember Muslims don't believe you can personally know God.
And as I said I do believe God says No, who am I or whose anyone to think God even has to listen to us? He never says He will answer all our prayers, or that all of them will be answered.
Every human being contains bias (you believe that from non-existence prayer is an abstract thought anyway, it that not bias?). Just because I'm a Christian now doesn't mean I always was. I was an atheist and study various beliefs and religions. I only have a narrow Christian view, when I have not always been a Christian? Bias? Everyone becomes or gets saved, it's something you chose right?
Why are you on a Christian website by the way? Made a wrong turn I think Starcrash