How to handle GSJ02 and WGS84 coordinate system in ios MKMapview?

Question

As I have done analysis, i got to know china using Gcj02 coordinate system. so I have some douts on below scenarios

So in my ios app I am using MKMapview and showing some location which I am getting in WGS84 format

1. If the location which l get in response is for mainland China and we shown as it as for outside china user will it show correct location or not? Or that is also need to convert in Gcj02?
2. In same case what will happen if user is also in mainland China(MKMapview will show as AMap) and location is also in mainland land china? Do we need to convert?
3. If user is outside china and location is also outside china then he can see correct location.
4. But when user in china(MKMapview will show as AMap) and location is outside china? Will that location displayed correctly?

As there are some converter classes available for wgs to gcj or vice versa

As per above scenarios if I have to use both GCJ to WGS and WGS to GCJ, how will I get know location is in which format?

Thanks in advance for your help!!!