Ola. Yes can do-in fact for the Swiss these are not ´small´ towns at all- Lausanne is among their biggest. Its also a very nice ride with splendid views over lake Geneva. Visit all 5 i 1 day will be a challenge though, even though they are not that far apart.

IN Swiss you can take about any train-there are some 30+ different train companies in all types of colours and names, but you canNOT use with EUrail the local trams etc-these also run on rails, but in the streets of town. Not the electric ´trolley´bus which serve as citybus in many towns.

Ohhh ok! So, in the cases of those trains that goes for example for Lausanne to Morges can I use the Eurail? Because I think that those one are considered not local right? 
 

ok, so I’ll do like 3 in 1 day and 2 more another day, what do you think? I’ll be staying in some hostal una Geneve. 

All of these places are on one of the main railway lines in Switzerland. And they are all in a row - if you go to Vevey, you'll go through all other places anyway. 

It's also possible to visit all these places by (steam) boat from Genève. Your pass gives you 50% off.

What’s your overall time for the trip? 
I think you are a bit in a rush if you do 3 in 1 day. 
Lausanne and Montreux are really beautiful (Vevey actually too) and you should definitely spend at least a day in Lausanne and Montreux - you can do a nice hike up from Montreux through a gorge and go back by train. Also you can go up to Rochers de Naye by rack railway (not included in Eurail, but maybe you get a discount?) for beautiful views on Lake Geneva.
In Lausanne you have the Olympic museum and also some other nice museums (the ones in Palais de Rumine should be for free even) as well as the lakeside with good restaurants etc. 
Between Lausanne and Montreux you can get off for example in Epesses and hike through the wine yards .
I spent overall more than one week in this area and still have not seen everything…

And also south of Montreux you have several beautiful castles (Chillon being the most famous but also the one in Aigle is really nice!) and in Bex you have a salt mine with a small train going inside the mine… :)