I received my Schengen visa, thanks to numerous Q&A found on this site. I have flights booked for in and out, and I'm considering to use Ryan Air to travel between a few cities.

I'm a Sri Lankan citizen with a passport that is not expiring recently. I have an ETAS SCHENGEN visa on my passport.

In the Ryan Air web site, this page says that non EU/EEU passengers should get their documents stamped by a special counter.

• Is it legal for a third party in general to stamp my passport? I understand immigrant officers can stamp it, and may be banks too when exchanging currency. But can a third party airline?

I should probably ask this from Ryan Air, but given their lack of support (as far as I can see), I thought to ask this on the people I love for traveling. That is you!

• Is this a one-time document check only, or do I have to go through the same procedure every time?
• Does this mean I cannot check-in online, and have to pay for their desk check-in every time, even if I wanted to do so online?