After having my 30 year old vacant house foundation repaired, 3 leaks in the cast iron sewer lines were detected and holes dug to expose them. 2 of the leaks are in the stack joints (larger than the 2 1/2 " pipe, bowl joints). The 3rd leak is in a 40' run of 2" cast iron from the kitchen/washer.
1. Can the stack joints be cut out and replaced with PVC?
2. Can the in line rotten pipe be replaced with PVC?
3. What are No-Hub Couplings and how are they used (minimum length etc.)?
4. Where can they be pruchased?
I live in Plano TX, 75075.

The No-Hub couplings can be purchased at any Lowe's or Home Depot, although what you really need for a proper transition from 2" cast to 2" plastic is a Mission or Fernco CP-200.

And yes, the stack joints and rotten sections of pipe can be replaced with PVC.

I agree with growler's answer. I would only add that there are 2 types of pvc now, regular schedule 40 pipe and foamcore schedule 40 pipe. While foam core is OK under a slab I prefer the regular schedule 40 pipe. It is heavier and more durable.