I guess that google will allow only the related sites or blogs to link exchange and if they ever found that you have exchanged links for payment or by illegal means, they will penalize your rankings immediately, so be very cautious when exchanging links and do it ethically!
yes google doesnt allow reciprocal link exchange but you can do oneway link exchange or two way link exchange or three way link exchange to develop natural link for your site. also Google consider this link as natural one way link.
I don't think google will allow it ,and if you want to do that, you will kill your google account . google want to get real customers for the ads, and if the they could not get it, they will not waste money in your account.