You can't downgrade, unless you restore your database from a backup taken when you were running v2.11.0 - and obviously you'll lose all changes you've made to the data since then.
Can you describe what problem you saw in v2.11.1 that wasn't in v2.11.0? I would say it's very likely to have been fixed in v2.11.4. Check the release notes for v2.11.2, v2.11.3, v2.11.4 for bug fixes. In any case I suggest you roll forward, not back.