I just share my thoughs
1. In term of 不 usually used for current or future situation
A: 你认识他吗?
B: 我不认识
I dont know
B: 还没认识
Havent known him yet. (Willing to know him now 😀)
2. B can say 以前没认识 cant say 以前不认识 (past)
But I just feel strange if someone only use 没认识 without specific context.
