In Game of Thrones, are the nude scenes broadcast, and are they done by the main cast?

in the Game of Thrones i saw 2 many Nude & sex Scene.

Whether there are "2 many" nude & sex scenes is subjective to the individual viewer.

i want to know are those scenes telecast in TV without censoring.

The original show itself was filmed without censorship. It is up to individual countries' broadcasting authorities & their laws to decide what to permit onto their own screens. The scope of censorship can range from none at all, to mosaic-ing body parts out, to cutting out scenes, to an outright ban of the whole show from any form of broadcast, and anything in between.

in that are the actresses real actresses or porn actresses??

Like Wad Cheber said, most actresses did their own scenes, with few but not no use of doubles. Are these actresses (or their doubles) porn actresses in real life? I don't know, I profess I do not follow the series. I'll need names for research to give you a more definite answer. Note: porn actresses, however bad they are at it, are still real actresses. Do not discriminate!

As an aside, you may be curious if they are having real sex. In general, sex scenes in non-porn acting doesn't involve real sex. However, sex acting involving penetration isn't unheard of in Hollywood, and is a small but gradually growing trend in recent years among some actors & actresses in the name of ever-improving realism.