>> We purchased swiss rail pass for Four days (from day 2 to Day 5) .
>> Day 3: Departure to lucern by normal train and then take a golden pass train from lucern to interlaken. Visiting interlaken in rest of day.
Interlaken is the least interesting town in the area. Instead of exploring Interlaken, I suggest you consider a trip to Mürren (free with Swiss Travel Pass) or a boat trip on Lake Brienz or Lake Thun (free with Swiss Travel Pass). This will depend on how early you get to Interlaken of course.
>> Day 5:Departure to Geneva , city tour ,lake sight seeing
Consider taking the Golden Pass route from Interlaken to Montreux and incorporating a cruise on Lac Léman (Lake Geneva) into this day. If need be (timewise), skip city tour of Geneva. Free with Swiss Travel Pass, but reservations on the Zweisimmen to Montreux sector of the Golden Pass route are recommended in July, and cost CHF 8 per seat. Reservations on the other sectors (Luzern to Interlaken Ost on Day 3, Interlaken Ost to Zweisimmen) might also be a good idea if you want 3 seats together, as the trains will be busy.
reservations.mob.ch/re servation/reservation/ reservation/reservatio n/reservation/reservat ion/reservation/reserv ation/reservation/rese rvation/f?p=151:1:32189086388788 91::NO:::
>> Q1 : Is it necessary to make a reservation in golden pass train in July month? Is golden pass train and normal trains have different route?
Reservations might be a good idea (see above). Normal trains also follow the same route as the official Golden Pass trains, but to find these services in the timetable for the sector from Interlaken Ost to Montreux, you need to put in "via Zweisimmen" to avoid getting details for the faster routes via Visp or Bern and Lausanne.
Q2 : In above said itinerary how much i need to pay at cable car or other mountain trains? Is it possible for us to travel in golden pass train from Lucern to montrex and return back to interlaken on the same day?
Titlis - 50% discount. Price information here:
Jungfrau - free travel to Wengen or Grindelwald; 25% discount between Wengen or Grindelwald and the Jungfraujoch. It's good to go up one way and back the other, as the scenery is very different for each route. Price information here:
www.jungfrau.ch/filead min/Prospekte_und_Bros chueren/Jungfraubahnen _Fahrpreise_Preisliste .pdf
Instead of doing a return trip on the Golden Pass route between Montreux and Interlaken Ost, you could incorporate this trip into your journey to Geneva on Day 5. Your itinerary as described above for Interlaken does not seem to have room for a return trip between Interlaken and Montreux in any case.