No. You cannot use 4g sim cards for making calls like Jio in Nokia 3310 (2017) model. However, if you want to use 4G sim card for making calls - then you can check Lava Connect M1 - which is a 4G feature phone and you can use it with Jio sim card. It also has support for WhatsApp and you can also use Facebook Lite in it.
Nokia 3310 Dual Sim variant comes with Mobile Phone, Battery, USB Micro Charger, Earphone and Quick Start Guide as in-the-box accessories.
Yes, you can change the display brightness in this phone.
No. You can not install WhatsApp on it.
Yes, Nokia 3310 does have a speaker available just beside the rear camera. Nokia 3310 does have conference call option.
There are a few things that do bring back the feeling of owning an original Nokia 3310, such as the classic Nokia ringtone, the physical buttons, the tiny body, and solid build quality.
You can buy other feature phones for less than this, and the new Nokia 3310 doesn't justify the extra outlay over the simple nostalgia card it's playing.