I have another itinerary in mind and I'm wondering how this can be done for as cheap as possible. I also I want to mention that I have a student ID and under the age of 26.

What I have in mind is the following: Amsterdam, Hannover, Berlin, Hamburg, Copenhagen, Gothenburg, Oslo, Stockholm, and Helsinki.

How and where can I book train fares for the Amsterdam to Hannover route? How much does it normally cost to take that route?

Is it cheaper to fly from Oslo to Stockholm or taking the train?

What's the cheapest way to go from Stockholm to Helsinki? Ferry or air?

Any budget airlines flying from HEL to LON? I did a quick search on Kayak for August 29th and Norwegian flies for US$80 to LGW. Can it get any lower than this?

Thanks for the help in advance!