The First Issue:

There is a difference between "substitution" and "alteration," as is evident from the previous discussion. This difference can be summarised in two aspects: 1. In terms of the nature of the issue: The one who substitutes claims that what they have introduced is the ruling of Allāh, whereas the one who alters does not make such a claim. 2. In terms of the ruling on the issue: The one who substitutes is considered a disbeliever by concensus of the scholars, whereas there is no evidence to declare the one who alters as a disbeliever.