Another possible answer is "I am not sure". I am not sure whether DL will accept it or not. Я точно не знаю, примет ли DL такой перевод.
Does "я точно не знаю" mean (1) I don't exactly know, or (2) I definitely don't know, or (3) both? Quite different meanings in English : 1 is not claiming precise knowledge (but I may know a little about it), 2 disclaims all knowledge of the answer.
How about the translation "I definely do not know" (In the sense of "I am sure that i do not know")?
Конечно, не знаю - откуда мне знать? (Of course, I don' know - why should I?)
I thought of two translations for this sentence: 1: I don't know exactly. In other words, I know, but not exactly... we may be talking about the distance to somewhere, and I know approximately, but not exactly.. but I do have some definite (but not exact) knowledge of the subject. 2: I don't exactly know. This means that I have some knowledge that I believe might be true, but I'm not sure. So I may think that I know the exact distance to the next stop, but I'm not sure about it. So, rather than knowing, I think that I may know.
Would both be written the same way in Russian?
Frankly, I don't see much (if any) difference between 1. and 2. I would translate the given Russian sentence into English as "I'm not sure." unless it is part of a bigger sentence: e.g. "Я точно не знаю, во сколько она вернётся" = "I don't know exactly the time when she comes back".
No. This sentence sounds weird and is never used . If you say it though, it is likely to be interpreted as «Я, кажется, знаю, но не уверен(а)».
точно has numerous functions:
Adverb: то́чно • (tóčno) (comparative (по)точне́е or (по)точне́й)
exactly, precisely, accurately, definitely
Interjection: то́чно • (tóčno)
exactly!, yes!, bingo!
Conjunction: то́чно • (tóčno)
as though, as if
Adjective: то́чно • (tóčno)
short neuter singular of то́чный (tóčnyj)
то́чен, точна́, то́чно, точны́/то́чны