To push up through a given commit, you can write:
git push <remotename> <commit SHA>:<remotebranchname>
<remotebranchname> already exists on the remote. (If it doesn’t, you can use
git push <remotename> <commit SHA>:refs/heads/<remotebranchname> to autocreate it.)
If you want to push a commit without pushing previous commits, you should first use
git rebase -i to re-order the commits.