The Switch Keys depend on the ASPs. In case you have the same ASP for both Acquirer and Issuer, then the same set of keys can be used. In case the ASP is different for the Acquirer and the Issuer, then each ASP will have a different set of keys.
The bank needs to raise all the requests again for the respective product and sub-product combinations in which they were already live - as this is a major change in systems.
There is no separate process for Production Key generation. In every cflow request where the Bank needs to go-live, the request reaches Production movement stage after approvals from other NPCI teams – and here the Keys are generated and shared.