What year Cadillac steering columns are compatible for this car (Sedan)?

1994 was an odd year. It is the first year of the new platform used in the Sedan Deville and it was the first year of standard driver side airbags. Those changes mean that none of the earlier columns will fit. Then GM changed the security system for 1995 so that the system in the 1995 column will not work with the 1994 PATS system. As such you are pretty much stuck with the 1994 column if you want everything to work. If the issue is that your column has become loose, there are kits and videos online that show how to remove and rebuild the GM columns. They include the instructions that the OE information doesn't have in it.