No. You cannot use 4g network sim cards. You need to select 2G network for your sim card and then you can use it.
No. Samsung Guru Music 2 do not support CDMA sim cards.
Samsung B310 comes with 800 mAh battery. But it is very efficient. You do not require to charge the phone for almost 3 days with moderate usage.
Yes, you can do conference calls from this mobile phone.