Hi,
@anacheka , and a belated welcome to the Forum!
Responding in the order of your questions...oh, to keep things in context, I originate from USA...
1) Camino 1 in 2012, Camino 2 in 2014 - I texted my wife every night and shared pictures after I was back home. Camino 3 in 2016 - much as 1 & 2 but, in addition, put out a couple pictures a day via text messaging. The difference for #3 is that circumstances required I carry a "smart" phone. On #3 I had an international plan for 2 Gig a month.
2) Having carried a few phones over the years, here is what I know - - but I hope better informed people will let us know of any precautions - - as long as your your phone is compatible with basic GSM network requirements, you can make an emergency call. If your phone already works in Europe, you should be fine.
3) Plenty of wifi ("wee-fee" in Spanish, btw
) now. Rare in albergues in the Fall of 2012 , predominant by Spring of 2014. I can honestly say that I did not bump into a cybercafe a year ago. Maybe they are around but much scarcer than in 2012.
B