I dont think there is any restriction on posting questions. You can post anything.And giving credit depends on the questioner totally.On moral basis you should but the final call is totally yours.

yeah u can do that..
haan...if u take it from somewhere due credit should be given.

Sure, we need to gain more and there is no harm in posting good questions from other blogs. Infact it will help us in exchanging more knowledge.
About credit..well..it is totally the question setters choice..It is  not necessary to mention specifically from which blog it is taken(since asking questions in future from that particular blog will be difficult then as people may start following that one too)..you can just mention that it is a 'copied' question.

But, post the actual question, not just the link to the blog.

jo karna hai karle..no1 will stop you!!!!

Umm, I'd think it's best to give a link too original source.