In is an interlinear comparison of the 1896 and 1929 editions of the Evangelical Catechism. The order of questions was drastically changed in the 1929 revision, so the table below shows the questions according to the 1896 order.
The 1929 revision makes several key functional changes: it relocates the ten commandments to a subsection under the creed, it simplifies some language by removing archaic and technical terms when appropriate, and it removes a number of in-answer biblical quotations; opting instead for simple citations.
In substance, the revision sidesteps a few of the more speculative and controversial theology present in the old edition. It does not refer to the angels as the principal creatures in heaven and it does not say man lost God's image in the fall. Other omissions include a question and answer on the general vs. special (effectual) call and a set of definitions of the attributes of God. It may be reasonably assumed that the theology of the Synod had not changed, it was only judged that these topics were too technical for the catechism.
Other changes will be noted below by section.
Man's chief concern is changed from "the eternal salvation of his soul" to "to seek after the Kingdom of God and his righteousness." The first answer leans pietistic, the second answer leans to the social gospel. This second answer has the advantage of being directly lifted from scripture, though it is not there called man's "chief concern."
The subsequent introductory questions are also all-new as a result of this change in answer 1.
In the 1896 version, there were two to four questions on each commandment. Awkwardly, the first "question" for each is not a question at all, it's a statement: "Rehearse the # Commandment." The 1929 version simplifies this by standardizing just two questions for each commandment: "What is the # Commandment?" and "What is meant by the # Commandment?"
The 1896 groups God and his attributes in a section with the creed, while the 1929 separates these.
The 1896 answers that God is "Life, Light, and Love; and therefore eternal, unchangeable, omnipresent; true, omniscient, all-wise, holy, omnipotent, just; blessed, good, gracious and merciful." It then defines each of the attributes.
The 1929 simplifies this and leaves the responsibility to the teacher to define terms as needed off-page. Each statement of identity (life, light, love) is given its own Q&A and is linked to certain attributes (eternal, unchangeable, ever present).
The 1929 adds the questions "What is the First (Second, Third) Article of the Christian Faith". It replaces "what grows out of original sin?" with the question "What is sin?", and it breaks apart each summary question into four.
(1896) What is the substance of your faith in God, the Almighty Creator?
I believe that God has made me and all creatures; that He has given me and still preserves my body and soul, eyes, ears and all my members, my reason and all my senses, also food and raiment, home and family, and all my possessions; that He daily and abundantly provides me with all the necessaries of life, protects and preserves me from all danger; and all this he does purely out of paternal and divine goodness and mercy, without any merit or worthiness on my part. For all this I am in duty bound to thank, praise, serve and obey Him. This is most certainly true.
(1929) A Summary of the First Article of the Christian Faith.
What has God done for you?
I believe that God has made me and all creatures; that he has given me and still preserves my body and soul, eyes, ears, and all my members, my reason and all my senses also food and clothing, home and family, and all my possessions.
What does God still do for you?
God daily and abundantly provides me with all the necessaries of life, protects and preserves me from all danger.
Why does God do this for you?
God does all this out of sheer fatherly and divine goodness and mercy, without any merit or worthiness on my part.
What do you owe God for all this?
For all this I am duty bound to thank, praise, serve, and obey him.
Here the 1929 makes its only three additions: "Why is prayer necessary?" "How should we pray?" and "Are all our prayers answered?"
This seems to be the most untouched section. There is one slight change that involves a complex debate, the question "Who, then, receives such Sacrament worthily?" is changed to "On what condition to we receive the blessings of the Lord's Supper?" This change is a loosening of the view on the Manducatio impiorum. By only stating that the blessings are for those with true faith, and not defining who receives the body and blood objectively, the 1929 catechism is made more compatible with a Lutheran view and less of a strict Reformed view of communion.