INFJ and INFP share three letters and a reputation for being sensitive, private, and idealistic, which is why so many people get one on Monday and the other on Friday. The letter that differs is J versus P, and it shows less in what you value than in how you handle the day: whether you close things or keep them open.
INFJ wants the plan settled so the feelings can be safe; INFP wants the feelings honored, and the plan can wait.
The only letter that differs is J versus P.
Most people who get both are strongly I, N, and F and sit near the middle on J/P, so a slightly different mood or situation tips the result. The tell is context: many people run J at work, where deadlines force closure, and P at home, where nothing does. That is not indecision in the test; it is two areas of life asking different things of the same person.
On a one-type test, no; on your scores, very often yes. If your J/P score is close to the middle you will get both, and the useful question becomes where you lean J and where you lean P.
Yes. Advocate is the nickname some tests give INFJ, and Mediator is the nickname for INFP. The comparison is the same one letter.
Then that is exactly your pattern, and it is common: structured where the environment demands it, open where it doesn't. A four-scenario result shows that split instead of averaging it into one label.
The four-scenario test scores each area of your life on its own, so instead of one label you see where INFJ shows up, where INFP does, and which letter is doing the moving.