There’s a lot of countries in the EU that are not using the Euro. The UK obviously was one of them. There’s also Denmark and Sweden, and a bunch of other littler ones.
Yes, but I believe it is now a requirement for membership of new countries, they will have to eventually adopt it -
Of the Member States outside the euro area, Denmark and the United Kingdom have ‘opt-outs’ from joining laid down in Protocols annexed to the Treaty, although they can join in the future if they so wish. Sweden has not yet qualified to be part of the euro area.
The remaining non-euro area Member States are among those which acceded to the Union in 2004, 2007 and 2013, after the euro was launched. At the time of their accession, they did not meet the necessary conditions for entry to the euro area, but have committed to joining as and when they meet them – they are Member States with a ‘derogation’, such as Sweden.
http://ec.europa.eu/economy_finance/euro/adoption/euro_area/index_en.htm