This walks you through making your last 4 commits look like freshly made commits, with new timestamps and commit hashes.
Step 1: Start Interactive Rebase
git rebase -i HEAD~4
In the editor that opens, change all pick to edit like so:
edit abc123 Commit message 1
edit def456 Commit message 2
edit ghi789 Commit message 3
edit jkl012 Commit message 4
Save and close the editor.
Then, for each commit, Git will pause and let you amend it. Run the following:
GIT_COMMITTER_DATE="$(date)" git commit --amend --no-edit --date "$(date)"
git rebase --continue
Repeat for each of the 4 commits.