When we consider where this 'permission' comes from we can answer points 1. & 2. First, every molecule in the universe, in a sense needs permission to do anything, because God is infinite in power. An infinite God can not allow anything to be done, without his permission. Therefore, for the Devil to exist, he needs, in a sense, God's permission. However the permission you are referring to is an abstraction from that more general permission and pertains to God's particular sovereignty, in rare specific cases. Here we are really dealing with God's sovereign control over the universe and we can have a window into it by this verse:
And we know that in all things God works for the good of those who love him, who have been called according to his purpose. For those God foreknew he also predestined to be conformed to the image of his Son, that he might be the firstborn among many brothers and sisters. And those he predestined, he also called; those he called, he also justified; those he justified, he also glorified. (NIV Romans 8:28-30)
(I have posted some details about this verse here, which supports this post, if you are interested in more details.)
This takes care of (1.) because for the elect God has planned out his blessing from eternity, so there can be no point where the Devil is not 'bound in chains' (Mark 3:27, Rev 20) in terms of the limits of his cruelty which he can unleash upon the elect.
With regard to (2.) I would say that the Devil is also clearly under the chains of God to limit his ability to inflict cruelty, otherwise, the whole world would due dead, or worshipping him, or some other great evil which we could not imagine. However this is a different case because he already has permission to rule their minds as he is the prince of darkness and ruler of the world.
The problem with all of this is our understanding of 'permission'. In general the Devil does not seem to need permission to carry on his work, but as he runs into brick walls of protection by God, he is bound. He is sort of free to cause havoc, without every second running to God for permission.
Be self-controlled and alert. Your enemy the devil prowls around like a roaring lion looking for someone to devour.(NIV 1 Peter 5:8)
However, in very narrow cases, such as Job and Peter, the Bible moves into a special circumstance when God seems to remove part of his protection for mysterious purposes that align with the Devil's wishes. These mysterious cases are called a kind of'permission' with Job and Peter. usually the Bible does not indicate that the Devil is asking God anything, but Job and Peter are on God's and the Devils radar specifically, so there cases have special attention in the bible. In fact God is the one who brings up Job! But these specific cases are still examples that not only work out higher blessing in those two person's lives (Romans 8:28-30) but draw out principles for us all who read them.
It is not really in line with scripture to think of the Devil as asking special permissions all the time, and God sometimes granting them and sometimes not. Rather God has generally granted the Devil to go about as he pleases under strict limits, and sometimes let's him go a little further when it suits God perfect will in working our his mysterious purposes in peoples lives and manifesting his glory to men. Both Christians and non Christians are i this open field of spiritutual warfare. Since this is the landscape God also wants us to enter into the conflict because it is not all going on without the effect of our own choices and decisions. We are to wrestles and pray because it makes a difference to the level of 'protection' we have obtained. This protection is primarily from sin. Therefore we are to 'wrestle' that means constant, tiring close contact, unlike boxing, or shooting.(Ephesians 6:12)