No. We often see ourselves differently than how other people view us. We have skewed and manipulated views on how we actually are. Personality tests can give you a general idea, but by no means are they completely accurate.
These tests are fun for RPing characters, but for yourself? No, not reliable at all.
I recommend going to a specialist and taking an IQ test, it takes a few days to be concluded and offers some insights. I did it once when I started therapy and I heard some cool stuff and few unconfortable truths. I think the IQ itself is a bit of bull, measuring intelligence with numbers is a faulty concept, but the personality part of the exam was pretty valid. It was useful and now I've grown as a person, and I think it is far more accurate than any online personality test.
I'd say "reliable-ish". The results are definitely a reflection of who you are, but they can be influenced by a lot, like your mood or if you see yourself as different than who you are, and I also think that it's important to remember that your experiences and growth constantly change you as a person, and so if you took a personality quiz 5 years ago and still use the label that it gave you, you might not actually be the same person you were back then. I've used the same MBTI personality-type test multiple times and while I usually get a similar answer, I usually end up changing one or two letters each time.