Re: how I can get answer of my security question
My guess is that you are having a problem with password recovery. (Your message is less than clear.)
There is a bug in Netgear's implementation of password recovery on some devices. You can get locked into a closed loop.
If password recovery is enabled, but you have not set the answers to the questions, it keeps sending you back to the beginning of the process. If you haven't already given the thing your personal answers, they are not in its memory and it has no way of knowing if they are correct.
If the standard factory password (password) does not work, then you will have to factory reset the thing to get back to that. Then either disable password recovery (check the manual for your device) or provide some answers to those questions.
Just another user.My network DM200 -> R7800 -> GS316 -> PL1000 -> Orbi RBR40 -> Orbi RBS50Y -> RBS40V