The question implies that there are 3 instances of SQL Server (ABC (Default), ABC\First and ABC\Second). With Replication set up between ABC and ABC\First, the removal of ABC\Second may not have an impact. There is nothing pointing in your scenario between ABC\First and ABC\Second so the removal of ABC\Second should have absolutely no impact.

The way your anser is written, ABC is the name of the server, and ABC\First and ABC\Second are the 2 instances of SQL Server. Thus, you cannot have replication between ABC and ABC\First. Thus, the answer would still be nothing because you cannot have replication between the server and an instance so Replication cannot be installed. Thus the replication must have been installed between the 2 instances, and now your answer is correct.

In addition, please see the remarks above about the various editions and how they work.

This is a very poorly described scenario.