Yes, LG G6 does have hybrid sim slot. So, either you can use 2 sim cards OR 1 sim card & 1 MicroSD card to expand the memory. You can use upto 2TB MicroSD card.
During our tests, it took about 75 minutes to fully charge the phone - from 0% to 100% battery.
No. LG G6 battery is non-removable.
Yes, the Indian variant of LG G6 does have hifi DAC - which produces excellent audio output even on normal headphones.
The LG G6 is still a decent phone if you can find it cheap.