Hi Miralyn,
Honestly skip Rome and just go to Venice. You can do Rome on another trip. Why? Because as everyone knows, Venice is a sinking city, and is completely full of tourists most times of the year. Except January, where it is slightly less crowded. So it's actually the best time to go to Venice.
Rome you can visit any time of the year.
While I agree that it takes time to appreciate each city, I do not agree with two days; two days in any city is NOT doing it justice. It's not Singapore you know. I presume your "two days" means one night; if so, it's definitely not enough. You'll hardly get to see anything. Consider at least three nights at each city.
There is no need to be kiasu and do as many cities as you can. It's not a competition. This is not the time to be Singaporean.
Well it's up to you of course but what I'm suggesting is to me, cheaper, less hectic, and a much better use of your money, rather than rushing here and there and not really seeing anything in the end. Remember also that the countries you are going to all speak DIFFERENT languages. You intend to learn German, Czech, Italian, and French all in one trip? Probably not, since most couldn't be bothered; but if you only needed to learn one or two languages it is at least doable.
It's your homework to Google around to find the prices of trains and flights. Be a good student lah. You don't expect the teacher to do all the work for you right?
The places you mentioned in Paris are all worth visiting. Each attraction takes at least half a day (don't forget you have to QUEUE up to buy tickets!); further adding to my point that it is just not possible to do all that in two (full) days.
I do not know about the two flea markets you mentioned though as there are literally dozens of them in Paris; the only one we went to was the Bastille marche on Sunday mornings. That one is quite large and is only frequented by mostly Parisians since it is not quite in the centre of the city. Anyway it is good that you already did some research; keep it up and post your findings queries here.
The best and cheapest way to travel around the city is by the metro.
With regards to locations of the tourist attractions and various airports, please check out the many map sites;
http://maps.google.com if you have no idea where to start.
