vijayramraj, do a Search (top of this page or in the menu on a phone) and you'll see a lot of threads about river cruises.
We did a Viking Rhine cruise Amsterdam to Basel, Switzerland. It could be done in reverse as well. We enjoyed it very much, They sell out months in advance so act quickly. They are all small cruises with just a 100-200 passengers, not like the giant ocean cruises. There is not much to do on board but eat and drink.
No, I don't think an expensive room is worth it. Almost all the cruising on this trip was done at night so that you have the whole day at your next port. The exception is the Middle Rhine gorge area, the part they show in the commercials. This is done during the day because it is very beautiful with castles and vineyards. So you'll want to be on the top deck for that part, not in your room. The rest of the River is kind of flat and industrial and not that scenic. It's the towns and excursions that make the trip worthwhile. At night, a lot of time is spent going through locks on the river, so you might wake up and open the veranda, and see a concrete wall 6 inches in front of you. You are also low relative to the river, so you dont get a lot of long-distance views. So that's why I say its not necessarily worth it for an expensive room.
No cruises go up the mountains, so I'm guessing you mean add-ons or excursions to visit the Alps. The tour extensions offered by Viking for early days in Amsterdam or extension to Luzern, are very very expensive, but can easily be done on your own if you know how to use trains and make your own hotel reservations. We did three extra days on Luzern which was a wonderful way to spend time in the Swiss mountains.
I would like to do another river cruise, but assume that the conditions will be similar. I thought Viking provide good service. They handled the airline reservations, met us at the airport, and helped us with onward travel.