Yes, you can even get pregnant if you use condoms, and take birth control...neither is 100% effective. When you have sex, you risk the chance of becoming pregnant, even with protection...although protection does lower the chances.
Yes you can still get pregnant.. its more liekly to be more effective if your on the pill aswell. Condoms dont always work as you may have a tiny split in the condom or it may be out of date, always check expired date.
Yes, no contraceptive is 100% effective. The only thing that is 100% effective is abstinence. I suggest using a hormonal contraceptive such as the pill or patch together with condoms. That way you'll be extra safe.
If the condom breaks , or has a hole in it , yes.