Hi, I wrote an open source project that may be useful to you!

https://github.com/dmuth/git-rebase-i-playground

It lets you create a Git repo with synthetic commits and has sample exercises for doing different things within that repo, such as removing commits or squashing commits. (along with hints and answers)

Building this project helped me understand the ins and outs of Git much better and I suspect there will be value for anyone else who works through the examples.