Regarding the white stuff, it is probably a combination of skin cells, oils and salts called smegma. It comes off, but because of its oil content, it doesn't just rinse off, you need to use soapy water. And if you do, it could irritate the sensitive skin under your foreskin, so be absolutely sure to rinse well. You can find a description of smegma on the Internet.
If your foreskin is not easy to retract, try not to worry. By 12 you should be able to see the tip, and by 18 it should retract fully. If you google the issue, (like, write "when will my foreskin be retractable?") there is a lot of good material about it online. Some pediatricians know very little about this question, my son's tried to pull back his foreskin when he was a baby! So look for a medical website when searching out information on this question.