>> 1) On the noon cruise from Lausanne on the heritage route of Lausanne-Lavaux-Montreux-Chillon-Lausanne, is it a good idea to get down at Chillon (even if we don't have time to explore the castle) and walk back to Montreux station along the lake?
Well, that's a personal preference, and depends on how much time you have. Chillon Castle is interesting to see from the outside, but it is much more interesting and atmospheric to experience the inside.
>> Google Maps says it's a 45 minute walk.
Yes, that's about right, at an easy pace.
>> Is it a hiking-type route or is it a lakeside promenade-type route? Basically is it a smooth walk?
Yes, it's a smooth, paved promenade.
>> My idea was that walking along the lake would give us better and different views of the castle and the surrounding area rather than returning to Montreux by boat.
It's a lovely walk, with beautiful lakeside gardens, but better in the other direction in my opinion, when you are walking towards Chillon Castle, rather than away from it.
>> Also, I'm assuming that if I want to get down at a certain port/stop then I'll only be charged fare for that much journey and not the complete return journey to Lausanne.
I've always travelled free on boats, using a pass, so I'm not sure whether you can get on and off boats in between your starting point and destination if you have a ticket instead. Hopefully someone else knows and can advise you.
>> 2) As I earlier reported, CGN gave 2 different prices - 1st and 2nd class - for the raclette gourmet sunset cruise that otherwise only has a uniform 1st class available according to their website. So what does the 2nd class mean in this scenario? (None of the 2 given prices - 1st or 2nd class - includes food/raclette)
I don't know I'm afraid. You probably don't get access to the restaurant if you are travelling 2nd class. However, you would need to clarify the details with them.