4 inch party wall or 2 separate 4 walls? / is my stud continuous?

[alphabeta2020]

https://photos.app.goo.gl/8y6rmxnJm4uooxdt6

question 1 is my stud(at location of (the party brick wall/stud /infill brick) continuous from foundation to roof?

Question 2 why don’t I see my neighbors floor joist ?

Question 3 does my neighbor have its own 4 inch wall to support their floor joist ?
is that the reason why i dont see my neighbor's joist ?

Question 4 Why doesn’t my (balloon framing ) party wall have a ledger board ?

Question 5 how thick is my party wall? Only 4 inches ?


More pictures

https://photos.app.goo.gl/aybJ5eod4Ksm7Coz9