u/AstronautMuted7097

I've been going back and forth on if this is correct, overkill, or wrong. I need to use the 3" drain (waste stack) to drain my toilet and sink upstairs while draining my washer downstairs.

Questions

1. Does the upstairs toilet need a 3" vent, or can I vent the toilet from the sink?
2. Does the sink drain need to connect under the toilet drain or parallel to it?

I appreciate anyone's insight. Please feel free to critique the layout if I screwed up somewhere.