Yes. A reduction fitting can be used.
I would use 3 inch for that.
A sewer "rod" is normally no larger then 3/8 of an inch diameter BUT a SEWER Cable can be as large as 11\4" even the small sewer rods can have large heads to maintain sewers as large as 36"
In Tulsa Oklahoma you can, but i would still use 4 in.
By placing the waste 2x the diameter above the opening
1/8" to 1/4" inch per foot.
A 3 or 4 inch pipe sticking straight up out of the ground? This is the clean out for the sewer line. If sewage is coming out of it, this means the sewer line is clogged or collapsed from there to the main city sewer. If you have a septic tank, the tank is full and needs to be pumped out.
In an inch, there are 16 lines. It should be the 12th line. From line 0 to line 12 is 3/4 an inch.
The standard sizes for toilet water supply lines are typically 3/8 inch or 1/2 inch in diameter.
i prefer 12 inch
First there should be no reason the a home needs a 4 inch waste line. Three inch is more then enough. But if you insist use a "consentric' reducer as opposed to the " "ecentric". Other wise your waste will have to jump up from the four inch , and you will have back up.
I have never heard of 3 inch, but I would assume it refers to the spacing of the hot and cold lines. Standard in the U.S. is 4 inch center to center.