I don't think so, IMO Google wants the end-user to 'understand' that the Adsense Ads are some kind of Advertisements/Sponsored Links which might contain useful information.
I wouldn't. as the others have mentioned it would be considered deceptive and you would lose your account.
I recommend you to read their policies first! https://www.google.com/adsense/support/bin/answer.py?answer=48182&topic=8423
No, you can't. Read this link so you'll know the things you need to avoid. http://www.quickonlinetips.com/archives/2005/05/15-common-mistakes-by-google-adsense-publishers/