"If God knows everything about you, why does he not hear prayer without the magic "AMEN" word"
Where does it say anywhere that He doesn't hear it without the AMEN?
"If everything is "in Jesus name" then why would God not know this every time and require that your keep reminding him"
IMO, this is more for us than for God. It is a reminder to ME that it is through Christ, my mediator, that God hears.
"If God knows your needs, without prayer, why pray?"
Again, this is more for us than for God. He will provide us all our needs, whether we ask for it or not. The sparrow doesn't pray and yet he's taken well care of. The exercise of us asking for assistance is what keeps us humble. Reminds us that we are the creation, not the God.
"If you pray out loud, doesn't the Devil hear you too and if so, isn't that like aiding information to the enemy?"
God is more powerful than the enemy, so no matter what Satan hears, I am safe. I've been saved and it cannot be taken away from me. So what harm is Satan going to do? If God's will be done, Satan isn't going to get in the way of anything.
Andi