Well I'm not gonna talk about Capital Punishment, because I'm much more interested in the real core of this discussion. That being: When is something that is said by the Church an immutable, unchanging and undeniable fact, and when is it an opinion, colored by the times and open to change, especially as the centuries pass?
The first one is easy.
In Roman Catholic theology, the Latin phrase ex cathedra, literally meaning "from the chair", refers to a teaching by the Pope that is considered to be infallible when an official statement on behalf of Church doctrine.Number two is almost as easy:
Roman Catholic theology divides the functions of the teaching office of the Church into two categories: the infallible Sacred Magisterium and the non-infallible Ordinary Magisterium. The infallible Sacred Magisterium includes the teachings of papal infallibility, of Ecumenical Councils (traditionally expressed in conciliar canons and decrees), and of the ordinary and universal Magisterium. (Despite its name, the ordinary and universal Magisterium falls under the infallible Sacred Magisterium.)As described above teachings which fall under the non-infallible Ordinary Magisterium are not dogmatic. It is a sin to eat meat on Friday is such a teaching. The sin is not to eat the meat, but to ignore the Churches requirement that meat be abstained from on Friday as a penitential act. But you get the idea. There are rules that the Church can change. As it did when it replaced the abstinence from meat with the requirement that some other penitential act be preformed in its place.
The order of the Mass under the Latin rite can be changed, as indeed it was. There are various licit rites for Mass. All are equally valid. In the past rites have been added and rite have been vacated. The Church has the right to make those kinds of decisions.
Now we get the the important part. That is that as Catholics we are bound to adhere to the teachings of the Church, those both dogmatic and non-dogmatic. It is permissible to discuss and even request change of non-dogmatic stands. And the Church can change those stands.
Since any catechism is likely to include information on both dogmatic and non-dogmatic teachings it is a chancy thing to use an old catechism as a source for what is dogmatic in the absence of other sources. More useful is to go to the original source material. The CCC is extensively footnoted, making it easy find original sources for teachings.
Bottom line: Follow the teachings of the Church. Work to know the dogmatic, infallible teachings, so you know where the hard lines are that way when a non-dogmatic teaching changes it won't seem contradictory.