As earlier you book single point to point tickets, as earlier you are.
but you are fixed on dates, times and trains. With Interrail you are more flexible.
So I suppose you will buy an Interrail Global Pass 5 travel days in 10 ?!
It is EUR 175 for YOUTH (under 26) travellers.
Paris - Avignon
- direct TGV train (journey time 3:30h), reservation required ( rail.cc/en/interrail-train-reservation/tgv-sncf/42
). If no reservation is available (limited seats for Interrailers), there is a non-official solution: rail.cc/en/interrail-train-reservation/tgv-sncf/42
- by free regional trains via Lyon. No reservation required. Journey time: 8 hours
Avignon - Interlaken
- using the TGV, reservations see above. Via Mulhouse and Basel. Journey time: ~ 7 hours.
- regional trains in France, then in Switzerland free IC trains. Via Lyon, Geneve, Bern. Journey time: ~ 9 hours. Free of reservation fees.
Interlaken - Colmar
- free train in Switzerland until Basel, from there regional train to Colmar. Journey time: 3 hours
Colmar - Paris
- direct TGV trains or with change in Mulhouse. Journey time ~ 3 hours.
- free regional trains via Mulhouse, Belfort. Journey time: 6-8 hours.
You will find schedules
Information about reservations
with Interrail here: rail.cc/en/interrail-train-reservation
And next time, please buy your Interrail pass here on railcc. Then you directly support this answer and all the information here on the website. And not just an anonymous big company like you will do with your purchase in Paris. As more people buy here, as faster the free answers are here.
We often send tickets to Russia without any problems.
Have a sunny trip, Peter