Senegal, Algeria, Sudan, Somalia, Liberia, Togo, Cameroon, Congo, Mozambique, South africa, Madagascar, Sao tome, Comoros, Seychelles, Mauritius, Cape verde.
Long names but the amount of borders cancels it out I think.
please post if you did better!
I don't know if the mainland can be done with fewer than 10 countries, but it can be done with fewer characters:
You have Congo, which will give both the Democratic Republic of the Congo, the Republic of the Congo and all their bordering countries. But just the Democratic Republic of the Congo is enough to get the job done; the Republic of the Congo is not needed as a separate entity. In that case, replace Congo with DRC, saving two characters. And replace Mozambique with Malawi, saving another four characters, for a total saving of six characters.
for the mainland. If I counted right, that's 57 letters, or about 2 a second with no mistakes.
Adding the islands means another 52, doubling the difficulty. Not to say that you must remove them from the quiz, or that you must extend the time, but be aware this quiz is twice as had with them in as with them out.
Took me about 10 tries and moment to look at map for plan