No. Vivo S1 does not have Qualcomm Snapdragon processor but it has latest the latest MediaTek P65 octa-core processor.
No. Vivo S1 does not have any association with Dolby sound.
Yes, Vivo S1 has dual 4G VoLTE support.
It takes about 2 hours time to fully charge Vivo S1 battery from 0% to 100%. Please note that Vivo S1 comes with a huge battery capacity of 4500 mAh. Hence despite fast charging support, it takes a little more time to fully charge the phone.