Macbook Pro is connected to wifi, but can't connect to internet?
So, after a while of talking with Apple CS, we found out that the problem was on the router side...
For the reasons unknown, the router wasn't allowing my MBP to connect it. I've reset the router 3 times(again), but my MBP still didn't connect but other device can(as I wrote earlier). So, I asked for replacement of the router... and voila! it's now working.
I've wasted so many times on this, but yeah, it works now.