not to worry, you've got plenty of time to get acquainted with paper 3. From papers 1 and 2, we know that Edexcel has only used the advanced information so I'd only look at the key question from 'Topic 1 and Topic 4' for me that's Sheriffs Robbers cave and Little Alberts study. Any research method can come up from the original full specification for paper 3. With issues and debates its tricky to explain, hopefully, your teachers have given you the rundown for what each issue and debate is e.g methodoly or nature/nurture. from there just use the spec. Also socially sensiive reasearch is a big one to learn, (its mentioned on the advanced spec). Good luck.