While I plan on hiring a licensed plumber to do this work, I'd like to make sure I understand the requirements as well, to ensure the job only needs to get done once

I have an existing basement bathroom which I need to tear into, to have some broken clay drain pipe repaired. Had the drain camera inspected and while 90% of the line is in perfect condition, there is some root infiltration right near where it ties into the new drain of the house, under the existing basement bath. I wanted to remodel it anyhow, so here's my excuse.

It's a small 4 x 7 foot space (finished floor space) and I plan on putting a 36 x 36 shower, toilet and small 18" wall mounted sink, (30" for toilet, 18" for sink on one wall, shower on opposite wall).

I haven't torn into the drywall yet, so I don't know for sure how things are vented, but everything is working just fine now (toilet and sink only).

I've created a diagram showing the location of the main drain under the floor and where I'd like to locate the toilet flange, wall sink drain and shower drain. I'd like to confirm the best possible configuration for connecting these to the main drain, with venting requirements.

Also, there is a clean-out at the bottom of the main stack - is it possible/allowed to 'extend' this clean-out port to bring it along side the shower, so I can have easy access to it? Or possibly I might need to install another clean-out on the horizontal drain under the floor with access beside the shower?

Any input provided would be more than welcomed. I have to confirm there is a proper vent running down to the basement to utilize - if not, I think my only option would be an AAV vent perhaps up in the cavity between the shower and main stack, made accessible by an access panel. I plan on keeping this area open and accessible, perhaps with narrow shelving for toiletries, rolled up towels or the like. I'll have about 8 inches between the 2x4 wall beside the shower and the wall of the bathroom.

Hopefully the diagram makes sense and people understand what I'm looking at doing

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