They do it on single engine in the US as well - the rating is an add-on to whatever licence you have and the checkride will be adapted to your own circumstances. If you take the IR checkride in a single you will have SEP/IR privileges. When (if) you do a multi checkride the examiner will include assymetric approaches and your IR will then have multi privileges.
Currency on an IR is a matter of keeping in practice or doing an ICC if you get out of currency. The FAA have no regular revalidation checkride requirements.