1) Due to careem, all small eco boxes have good resale these days.
2) Parts are available, both new and used, some readily and some on order.
3) I have a 7th gen alto, that does 17 with ac and 19 without ac, mine is without any eco technology, besides a cvt gearbox. But to be on the safe side, take 20 as an average of the fuel consumption of a good graded car.
4) Different variants with different options, there are cheap grocery two door models and there are expensive 4 door top of the line models with power mirrors, climate control, radar directed cruise etc.
Just to be clear, these cars aren't new, they are used..