[SOLVED] How to go back to an old commit, make some changes and commit those changes at the old commit which also updates all the following commits

How to go back to an old commit, make some changes and commit those changes at the old commit which also updates all the following commits

I was working on a file, I comitted some changes, then I realized that I want some of the changes I've made recently in an older commit, because it is a part of the older commit.

So, I want to go back to the commit 2c57de7 and add some of the changes that I've still not added to the staging area, in the same commit. I do not want to create a new commit.

I tried the Detached HEAD state, but then I don't know how to merge a branch after the 2c57de7 commit.
I tried the interactive rebase option by stashing my current work and the popping the work at the 2c57de7 commit and the resetting the commit so I could add the modified file. But I'm having a lot of merge conflicts. If there's an article about how to resolve merge conflicts, it would be extremely helpful!
I tried making a new branch, reverting that branch to that old commit, making the changes, and then merging the tip of that branch back, but it didn't work.

* 59939c3 - Sun, 16 Jan 2022 14:19:40 +0530 (3 hours ago) (HEAD -> main)
|           Problems - Added Problem 03
* 2c57de7 - Sun, 16 Jan 2022 12:52:04 +0530 (4 hours ago)
|           Problems - Added Problem 02
| * 3031e71 - Sun, 16 Jan 2022 13:37:14 +0530 (3 hours ago) (Trees)
| |           Level Wise
| * 7aaa1dd - Sun, 16 Jan 2022 12:44:59 +0530 (4 hours ago)
| |           Introduction
| * 5c26db8 - Sat, 15 Jan 2022 18:13:23 +0530 (23 hours ago)
|/            Vectors
* 692c42e - Wed, 12 Jan 2022 19:10:02 +0530 (4 days ago)
|           Problems - Added Problem 01

This is my commit history

Any help would be appreciated!

Solution

which also updates all the following commits

That means you would need to rebase those following commits on top of your updated old commit.

From your current main:

git branch tmp
git stash
git switch -C main 2c57de7  # reset main back to 2c57de7 
git stash pop
git add .
git commit --amend -m "Problems - Added Problem 02, amended"
git switch tmp
git rebase main
git switch main
git merge tmp
git branch -d tmp