First of all for a CPL the age limit is 18. So you have to wait to do your CPL exam anyway.
You can however start instrument training and as soon as you turn 17 do your PPL and IFR checkride.
All the hours you fly solo are of course PIC hours and of course they count. (There's nobody else to save your ass)
You can technically do your all your training without even taking the PPL checkride and do CPL straight away.