And here I am, thinking your name was a nickname in honor of Johnny Cash:banghead:
Nope. I post under my real name.
If it can be compared to it at all, what level would this be in terms of JLPT? I only ask to better understand the magnitude of this incredible achievement
Nothing that I can do can properly be called an achievement, much less an incredible achievement.
I really have no idea how the levels compare, and I strongly suspect that there is no good way to draw a comparison. This test assumes that people taking it are native speakers. Naturally, native speaking children who are in the early years of elementary school and taking the lowest levels are still going to be far ahead of beginning/intermediate foreign learners. I think the foreign learner
could potentially have an advantage on kanji, but will have shortcomings on vocabulary, unfamiliar grammar, lack of reading speed, and just general overall lack of breadth of experience with and exposure to the language.
You can see the opinions of some other foreigners who have taken the test here:
日本語検定 | 受検生の声 外国の皆さんより
One person says he is "almost" N2 and he took level 6. Another is of the opinion that N3 is about level 7 and that N1 is about level 4. I think one person says N2 is about level 5.
As I have remarked elsewhere, at some point for more advanced foreign learners the problem isn't breadth of Japanese knowledge but test time limits which are based on the reading skills of native speakers who were educated in reading and writing the language from early childhood and who have far greater reading experience than practically all foreign learners.
By way of comparison:
You can see that I missed the last question on the level 4 test. Like the JLPT, the big reading blocks come last. I missed the question because that's where I was when the clock ran out and I just marked the answer randomly. A month later I took N1. A common complaint is that there isn't enough time to actually read all the text....only to skim it. It is entirely possible that I didn't pass N1, but it won't be because I didn't have time to read; I read all of the texts all the way through at least twice and still managed to finish. Thematically, the JLPT texts were much more difficult, as the NK level 4 test is aimed at junior high graduates. I read Japanese fast enough to read through the N1 material twice in the allotted time but I was racing like mad and
skimming the much easier NK4 text....and had to do a Hail Mary on the final question. A 14~15 year old Japanese girl taking the same test finished more than ten minutes early. On the level 5 I finished ten minutes early and a woman I
think was also a foreigner didn't finish the reading section before time ran out.
There is a section on the test's website where you can see samples of the type/level of questions that appear on the test, so it is pretty easy to self-assess which level might be best to take. Unlike the JLPT, it is possible to take two different levels on the same day, meaning you can take one you're pretty sure you can pass and a higher one as a challenge.
The TL;DR there is "I don't think it is possible to make a direct comparison or correlation between levels of the two tests".
