Condoms you can get in a grocery store or in machines in cafés and such. But condoms and all the other forms of birth control are available at a chemist or drugstore.
Contraceptives is a name for various products that can allow people to have sex w/o getting pregnant. A condom for instance will not only protect against pregnancy, but also against STDs.
You CAN take them both but since they each come with side effects i wouldn't. The Injection on its own is very effective, as is the Pill. The difference however is the efficiency of the pill depends...