can I get off train in innsbruck instead of salzburg?

Yes.

I assume you will have a train specific, non-refundable ticket to Salzburg. Be careful, if you just happened to get off the train in Innsbruck, just to look around, and forget to get back on, and the train left, they would not let you go on to Salzburg. (Just make sure you take your luggage with you, wink, wink. I always do, even if just getting off the train to look around. Never know what might happen.)

And, you don't check bags on the train. It's not a plane.

Check your dates to ensure you are not locked-in to a specific travel date.We get off and back on to explore for 4 hours and then continue.If the train ride is 6 hours stop half-way like Innsbruck and spend the night.You may have to buy a ticket to Innsbruck and then a ticket to Salz.So what.The main thing is you know your destination and that is good!

Yes

I assumed from your question that you had a train specific, non-refundable SparSchiene ticket from somewhere in Italy to Salzburg and wanted to get off in Innsbruck instead. In that case, of course, you would have to use another ticket, which you would purchase, to Salzburg. I'm not that familiar with Austrian Rail, nor am I sure you can do this in Germany with a Europa-Spezial ticket, but in Germany, with a Sparpreis ticket, you can build in a stopover of a specific time when you book your Sparpreis ticket. I did that in 2008, when I stopped over in Köln for two hours on my way to Hannover.

Also, in Germany, if you buy a full fare ticket from point A to point B, and the distance is over 100 km, you have until midnight the following day to complete your travel.