Changing the underground sewer pipes - a few questions

I live in a brick house which has more and more “blockage” issues, which cause minor flooding.  The problem is that the pipies have really gotten narrow and we usually get something trapped in the “U” trap that connects to the city line, or in thre spot where seweage comes down from the 2nd floor and needs to connect itno the main line. The pipes are probably from 1930’s and my wife and I decided that we want to change them.  The good news is that we have had no issues with the city sewer main, so we need not to dig all the way out into the street.   Just replace everything starting from the trap at the front of the house (and install a sewer check valve on the city line) and until the back of the house trap, which connects to the backyard drain. The good news is that my basement is pretty much unfinished as what is there is probably from 1950’s.   It has been paved but we have nothing there.  Cutting the ground to get to the pipes will not mean I am tearing down flooring, walls, carpets, etc. My questions are 1)  When I changed my water supply from LED to copper, I did not need to file for any permit.  What about when I want to change the sewer lines (without touching any of the city ones)?  All of the work will be done under my house’s roof, and none on the sidewalk.  Here is the important part:  I am NOT changing any plumbing fixtures in the basement or anywhere else in the house.  Meaning that the new sewer lines will connect back to the same old fixtures.  Nothing is going to be added or removed.   I plan to re-do my basement in a couple of years, so that’s when I will upgrade all those. 2)  Since I am in Kings County (NYC), I understand that I still cannot use PVC pipes for underground sewers, is that correct?   I plan to use 4″ lines made from cast iron, which is made in USA. All advice & feedback is much appreciated.