A single code is generated for a travel day, adding or removing trains does not change the data from the code, just the text on the app displayed below the code.

In general the Android version of the app seems to work better and suffer from less bugs.

Sorry I was unaware about it, 

Can you please make clear if I am travelling on 1st May from, 

Geneva - Luzerne - Zurich 

If I first activate QR code for Geneva - Luzerne.

It's an 10 min transfer time, then I Generate QR code for Luzerne - Zurich, from Luzerne Railway Station is that fine, 

Or you mean to say for 1st may, I just need to generate 1 time QR code stepping in first train later its the same QR code for whole day even if I change 4 trains.

You need to add each train as a journey to your trip. This you can do in advance. Just before boarding the train you activate the journey.

The QR code will be the same for the whole day, but there will be a list showing all activated journeys (trains) below the QR code. The train you travel with has to be on the list below the QR code otherwise you don't have a valid ticket. 

Thank you friend, i hope every thing goes well.