codes for drain lines

I am in the process of renovating our bathroom and after ripping out our fiberglass shower, I came across the drain vent pipe that is unfortunately placed on the shower side of the wall. One plumbing company said they could charge around $600 to move it a few inches so I can tile the wall there...

I have a toilet drain that has 3 x 3" 90 degree bends back to back. The other toilets in the house have the same number of bends, but more spread out. Can anyone tell me if this a code violation in Ohio? Thanks in advance.

Have a look at this pic and tell me what's wrong...Please...and what would be up to code THis is a bath sink drain. the pipe coming through the wall on the left is coming from a kitchenette sink onthe other side of the wall... I just want to know if there is any way in hell that is code, if not...

So as you can see in the images below my sink drain is really close to my drain line so I have no idea how I could install a drain line for a dish washer. I'm thinking maybe if I get a smaller drain I may be able to fit it but I don't that I could find anything that would be so much smaller that...