You are required to submit to a background check upon acceptance to a majority of schools, if you follow the link below you can get some FAQs about what all that background check will entail. I would definitely recommend making it known if possible, as you could end up immediately forfeiting an acceptance offer if an institution were to discover anything that you did not identify.
Yes, you are required to report any disciplinary action from undergrad. This is not part of the formal background check. It is either included on the OptomCAS application or either any of the supplementary applications, pretty sure part of OptomCAS. Do they call your uni and verify? I don't think so. I would not advise lying about this, as if you were caught I'm sure your application would be denied.