Yes, you can use all trains run by DB and trains run by many of the other railway companies in Germany.

Here you can check what railway companies that are included in the Interrail/Eurail offer:

https://www.interrail.eu/en/plan-your-trip/tips-and-tricks/trains-europe/railway-companies

If you are going to travel during the summer, when you can use the 9 EUR ticket in Germany, and if you only are going to visit the towns mentioned above, it might be cheaper to buy ordinary tickets, than buying a global pass. You can calculate on that using the national railway companies' websites.

The ferries between Stockholm-Tallinn, Tallinn-Helsinki and Helsinki-Stockholm are discounted with the pass. The discount is on the ordinary fare so it might be possible to get a cheaper ticket without using the Interrail discount if you book well in advance. 

Thanks a lot for the quick response.  Do you know if I need to pay the difference for using ICE or IC?  The 9€ tickets can only be used on regional trains and not ICE or IC.  A trip from here to Flensburg takes more than 8 hours and I need to change trains 4 or 5 times with the regional train!!!  The price of the pass is €365 for 10 days, I believe it is cheaper than buying a separate ticket, or?  besides saving time....

If you want to use the IC and ICE you need a global pass. I have not read anywhere that you can pay a difference from the 9 EUR ticket to travel with those trains. I guess that you are right regarding the price and the time saving aspect of the global pass.

You helped me a lot.  

Thank you very much. 

Roberto 

In DE DB runs ALL IC/ICE trains-besides them there is a budget FLIXtrain (Green trains) but this wont help you. It may be in some cases that In DE the train is a swiss or Austrian one-or going to DK a DSB=danish, but INside Germany its considered to be DB.

I have this 9€ ticket and used it: forget it, trains are so overcrowded you will have to satnd at least half that way using it.

thank you very much for the answer.... You are right, besides being slow and stopping in many small train stations, the 9€ ticket for the next 3 months they will always be very full... I will make the plans and check better which ticket should i buy.  Thank you very much.