How to drain kitchen sink through bathroom drain

Question

In the basement bathroom our vanity, toilet and tub are on the same drain line. As in this picture.
The vent for these pipes is connected between the toilet and the tub.

We want to create a new kitchen in the unit above it. Since the bathroom is directly below it. Can we connect the sink drain to the bathroom drain (the main drain line) as in this picture?

This means we have to dig the concrete to connect the kitchen sink to the drain line of the bathroom. Can we connect between the vanity and the toilet?

Alternatively, instead of digging concrete, can we connect the kitchen sink drain to the bottom of the bathroom vent as in this picture?

Answer 1

You can buy it depends on the size of the vent below the joint must be 2" minimum because it will be a wet vent.