>> But I am not able to find the Boat trip from Thun to Interlaken. Can you please help me on it. And also can you tell me the last boat departing time from Thun to Interlaken ?
You can find the boat timetables here:
There are different timetables for different times of the year, so be sure to look at the appropriate one.
>> Do we need to make any reservation for the Boat Trip , even if we have Swiss Travel Pass?
No reservations are needed (or possible).
>> Interlaken OST to Scynige Platte ... It seems the last train from Interlaken OST is at 16:35. Can you please confirm , there will not be any trains or transportation after that time?
That's right. The 16:35 departure from Interlaken Ost is the last one that will enable you to get up to Schynige Platte.
If you take that connection, you will get to Schynige Platte at 17:37, and the last train down from Schynige Platte is at 17:53 so you would have only 16 minutes there. There is a 200-metre gradual uphill walk from the station to the viewpoints, so all you would be doing is rushing up the hill, taking a few photos and rushing back to the train.
If I were you, I would go up no later than 15:35.
>> Interlaken OST to Murren: Whether this route is covered as part of Free travel with SWISS Travel Pass covers or Do I need to get separate ticket (where I will get 25% discount) ?
Interlaken Ost to Mürren is free with the Swiss Travel Pass. Lucas provided a link to the Swiss Travel Pass validity map.
If you download that, your questions about where the Swiss Travel Pass is valid will be answered. As explained in the legend on the map, red lines are trains, yellow lines are buses, black lines are cable cars, white lines are boats. Solid lines are free, dotted lines are discounted. Discounts are mostly 50%, but only 25% for transport where you see the number "1" inside circle near the dotted line. There are a few grey lines on the map as well, which indicate transport that is not covered by the pass.
>> Whether any reservation is required for this Section of the route.
>> Murren to Wengen: Whether this route is covered as part of Free travel with SWISS Travel Pass ?
>> Interlaken OST to Brienz via Boat and then to Luzern. Is it possible to board the boat with our luggage (including one big suitcase) ?
>> Assume , this boat will be covered as part of Swiss Travel Pass (with free of cost) .
>> It would be really helpful, if you can share any link or information on the availablity of Public or Paid toilets (Wash Room) in Wengen , Luzern etc.,
> Wengen railway station: downstairs, at the back of the station. If I remember rightly, they are free.
> Mürren railway station: half way up/down the stairs. Free, if I remember rightly.
> Luzern station: take escalator down to the level below platforms. Attendant, fee payable.
> Brienz: at railway station. Coin in slot, 1/2 Franken coin (as at Sep 2016).
In general, there will be toilets at railway stations and mountain-top restaurants, as well as at many cable car stations etc. Look for the WC sign, or ask for "WC, bitte?" - pronounced approximately "Vay Tsay, bitteh". Damen is ladies', Herren is men's.