other approach is using ilspy from icsharpcode, github, it also lists my binary requires .net2 framework to run
Now interestingly, dotpeek, jetbrians says that my binary was compiled with .net framework 3.5 but will run with .net 2 framework. This extra information about .net 3.5 is not available in any other tools.
Anyway, found the information i was looking for. But it is quite interesting that dotpeek could infer more that other tools. Not sure where it found that information- but something to find out i guess..