You're going to edit it ten times or more before you send it off for publication in all likelihood (that's based on other published authors I've talked with). If you aren't prepared to do significant rewrites and possibly get rid of quite a bit of previous effort going in, you might be fighting the wrong battle. Additionally, as you write, your grasp of the character voice changes significantly. You get better at being in his or her head, exploring his or her motivations, knowing instinctively what she or he would do when in a particular situation. Your character becomes more consistent through exercise.
You can go back later to modify the age of the character, the setting, or other details if you must. But you'll get more secure in voice as you write. I still contend that if you focus too much on editing now, you risk not finishing it.
If your concern is that you can't make a 14 year old sound realistic in the first two chapters, when you aren't secure in the character's motives, reactions, or voice, I wonder if constructive criticism really is what you need. The most that is going to offer is the subjective view that "that doesn't sound genuine" to me. Ideally, you need to go out and meet some 14 year olds...
Re: Need critique on a basic point
You can go back later to modify the age of the character, the setting, or other details if you must. But you'll get more secure in voice as you write. I still contend that if you focus too much on editing now, you risk not finishing it.
If your concern is that you can't make a 14 year old sound realistic in the first two chapters, when you aren't secure in the character's motives, reactions, or voice, I wonder if constructive criticism really is what you need. The most that is going to offer is the subjective view that "that doesn't sound genuine" to me. Ideally, you need to go out and meet some 14 year olds...