Frequent asked questions about the Kristians route
Also take a look at Practical, which may already have some answers to your questions.
Do I need to make reservations for taking my bicycle along in the train or the bus?
If you want to assure yourself of a place for your bicycle, making a reservation is recommended.
Through the app Entur or the website of Vy, it is relative easy to buy a ticket. In Oslo you can also buy tickets at the counter. The train station of Kristiansand and all stations in between, are unmanned. Ticket vending machines are available.
Sometimes you may need to make a reservation for the bus. Check the site of the concerning bus operator. If there is room, the bicycle can come along. The driver determines if the bicycle can come along or not, even if you have a reservation. Sounds like it is unclear, and frankly it is. In short: just try it. You already have a 'no', but you might get a 'yes'.