Yes, Moriendi
4K -> X8(1) is good.
4K -> X8(2) is good.
But X8(1) -> 4K -> X8(2)is bad.
I have connected one Panasonic NS1000 with 4K over PRI,
X8(1) <-> 4K <-> NS1000 is good.
X8(2) <-> 4K <-> NS1000 is good.
No network codes, digit suppression, prefixes needed.
About NNO, DNNO and DESTNO, Can...