For #1 its different-there is a special supplm of 10€ to pay-if you forget it, the conductor will ask for it, this is for all trips into/out of  ITaly to Austria.

oh

@mcadv 

first of all thank u for answering

So ok ill pay 10 euro but a question too

is the train wants any resv? Or as railapp says no resv req?

thank u again appreciated man

@mcadv 

and also the trains which i wrote above does any of them want a resv if u know? cause app says no resv req any of them

No reservation needed. The 10 euro supplement you can pay to the conductor when he checks the ticket.
Sometimes you are lucky and they don’t come :D

@mcadv

I paid it now for Venice Austria train 

Do i have pay that again in Austria and Hingary? Where? How many times?

How much did you pay? 10 euro? or 3 euro?
3 euro would be seat reservation and then you’d have to pay the 10 euro extra when the conductor comes for the ticket check.
For the other 3 train trips no reservation needed. Innsbruck to Salzburg will be almost empty one, Salzburg to Vienna as well (at least in the beginning, later there might be some commuters on the train if you travel during the week and in the last part could be then quite full).
Vienna-Budapest usually is crowded. In Hungary many people enter the train and the “last minute reservation”-seats might get occupied… little bit a lottery sometimes. But reservation not compulsory.

@MartinM 

i paid 10€ for venice innsbruck. just 10 then she gave me the ticket with my seat number.

Im gonna take the first train on salzburg to wien so as i unders. its empty.

About vienna budapest as u said if it will be full booked 

could i still get in the train or the ticket guy just kick me out what should i do about that?

thank you martin u are literally saving my life right now