Self-Studying APUSH?

Yes, colleges often see students self studying for exams, and you can record it as an ap test you plan to take on your common app without the class being on your transcript.

For ap classes that will count as credit for studying political science, it depends completely on the school. Some schools only give credit for ap classes related to your major (ex no credit for ap chem, since it’s not related to political science), some schools only give ap credit for courses not related to your major (ex credit for ap bio but not for apush because they want you to take your major classes from them), and some schools give credit for all tests.

I agree with @ajdekon. College credit from AP courses depends entirely on the college and its choices. But if you looking are looking to take AP classes that have correlation with a political science major, I suggest the following: AP World History, AP Psychology, AP Statistics, AP Government and Economics, AP Language and Composition and even AP Calculus. As far as your question regarding Spanish, I cannot say for sure. Going all the way up to Spanish 4 definitely holds merit, but I'm not sure that it is more impressive than taking an AP Spanish course. Think of it this way: a regular English 3 or 4 course is not as impressive as say, taking a AP Language or AP Lit class.

:)