The following command from your terminal lists all the commits yet to be pushed to origin:
git log origin/main.HEAD
If needed, replace main with your current branch name. This command shows you all commits on your current branch that aren't there on the given remote branch.
To know if a particular commit with hash COMMIT_HASH has been pushed you may use
git branch -r --contains COMMIT_HASH
This should return a branch from the remote if this command succeeded and otherwise it failed.