Need to close off or move a vent pipe & drain that goes to nothing

Newbie here. I'm a DIYer doing a kitchen renovation in a house built in 1965 in Virginia. I found a pipe in a wall that I need to move or remove.

I am cutting down a full height wall to a half wall/peninsula bar. In this wall, there is a copper pipe (1.75" outside diameter) that goes from the roof (vent to outside) straight down through the attic, then thru my wall in question, where there is a capped-off Y-connection where it appears a sink/washer/some-other-water-appliance may have been. The pipe transitions to a slightly larger pipe (about 2") then runs straight down through the floor into a crawl space (with a concrete floor), then turns and runs to an exterior wall and transitions to a cast iron pipe and goes out the block foundation wall and into the front yard.

This pipe connects to no other pipes or anything else in the house. I am pretty sure the septic tank and drain field are on the other side of the yard about 50 ft away. The rest of the house's plumbing are on the other end of the house, too. This part of the kitchen is one story and the center part of the house is two story (three if you include the finished basement). Is it easier/cheaper to run a drain outside and tap into the septic vs running the pipe through the basement?

There were also two electric circuits (one heavy wire like my other 240V-40A circuits that was run to my panel but not connected to a breaker, one 120V-20A circuit still attached to a breaker) left in this wall (walled up behind drywall). Because of this, I think there may have been a washer/dryer here in the past.

Should I route the pipe around the open space above the open bar OR can I just cap it off and remove the pipe?
Is it possible that this vent pipe is needed to vent the septic or drain field?
Is it common to run a second drain out a new hole in foundation to connect to a septic?
I don't need the drain. My concern is that the vent may be needed. There are four other vents through the roof for the kitchen and bathrooms in the house. There's no water supply lines in this wall.

Thanks in advance for any help.
Jimmy