1.   I think it's great that you're thinking about how lasers work!  It shows you're really thinking about what you do and trying to understand as much as you can.  Remember though that when you're treating brown spots the target (chromophore) is the melanin not the cells themselves. The cells themselves aren't dying like they would for example with liquid nitrogen treatment.

The melanin is both outside and inside the pigment making cells (melanocytes).  It's the melanin that gets broken up into tiny particles that are carried away by scavenger cells from the immune system.   The cells that keratinize (mature) are called keratinocytes and they are a completely different cell type than the pigment making cells.  Hope this helps.

 2.   I'll get back to you on this one next week.