Finnish language is compulsory to survive in finland?

Hi this is bijo from india, presently working in bahrain and Im planning to migrate to finland with family,my wife is looking for nursing jobs there,
Before that wanna know more about finland .

Not sure where you plan to move to, but my experience is with Helsinki, so my answers are more for that area.

How cost effective is finland compared to other European countries?
Helsinki is probably about the same as most other larger European countries. It isn't cheap to live in Helsinki, and the cost depends on where in the city you want to settle. City center is going to be more expensive than some of the outlying suburbs. Be assured, however, that you can get to the city center with very little issue from outside the city.

Whether its easy to get a job for expat in the field of IT?
I don't have experience in IT, but I have read that the IT field is more likely to hire expats who don't speak Finnish. Unfortunately, most jobs advertised that I've seen require that the applicate speak both Finnish and English.

How good is the climate ?
It's Helsinki, Finland. November and February are miserable: rain, sleet, snow, overcast. Spring/summer typically lasts from May to August.
It's winter the rest of the time.
If you don't mind snow, December-January can be beautiful.

Rent for homes is medium or too high?
We rent outside of the city center, in a quiet suburb (Pihlajamäki), and pay about 800e for a 1 bedroom apartment, about 55sqm

How to obtain the driving license ?
For me, it was a matter of turning in my US license for a Finnish one. I had to fill out a form, have two witnesses attest that I had been driving in Finland for a year, and pay something like 50e. That was easy. It might be different coming from India.

The finnish people are understanding?
Generally, I found Finnish people to be quiet, and they like to tend to themselves. However, having a dog was enough for many of them to open up, and give us something to talk about. But generally, Finnish people are quiet around strangers. It does depend on the person, but most (not all) are not in to 'small talk'.  Most Finns under the age of 50 speak English pretty well, although I do try to speak Finnish when I know the word(s), but I haven't found it absolutely necessary.

Finland is lovely, and has a lot to recommend it. However, Finland is also in the midst of a recession and is having a tough time economically. The unemployment among native Finns is high enough, and among expats is even higher. Chances of finding a job by just being in Finland is pretty low, unless you have a highly sought after skill. IT people are pretty common in Finland, given the layoffs in the industry. Your best bet is to have a job when you get to Finland, rather than hoping to find one when you get here. Housing is getting more and more expensive as there are more people looking than there are available units, and so the prices are going up all the time.

Hope that helps.