All countries associated with the European Broacast Union can participate.

Theoretically yes, but associated members (in contrast to full members) still need to be approved on a case by case basis.

Active members (as opposed to associate members) of the European Broadcasting Union (EBU) are eligible to participate; [...]. Associate member broadcasters may be eligible to compete, dependent on approval by the contest's reference group.[49]

https://en.wikipedia.org/wiki/Eurovision_Song_Contest#Participation