No

The different numbers not cumulative.  If you install 2.0 you can still get some application refusing to run unless you install 1.0, and etc.

So, sure, you can uninstall whichever ones you want.  But you should only do that if you dislike Microsoft and using the .NET framework so much that don't want it on your computer anymore.

While I guess we shouldn't be surprised, since it is Microsoft, it appears each version of .NET supports different functionalities.  Despite the numbering scheme which would lead any sane person to conclude that 3.5 was a cumulative upgrade or update to 3.0 or 2.0 or 1.0, that ain't the case (from what I've read & been told by others more knowledgeable than me).  Moreover, you may not have any applications that use any of the versions.  Far as I know, there's no way to tell, though there may be, until you get some sort of error message telling you that an app requires .NET x.x.

Yeah, all implementations are non-cumulative due to the changes making previous versions programs incompatible.

this was definitely what i was also thinking. a simple No would do for an answer to your question.