This paper presents exact analysis of interference probability and outage probability of underlay cooperative cognitive networks under quite general conditions such as imperfect channel information, maximum transmit-and-interference power constraints, correlation among received signal-to-noise ratios and non identically distributed fading channels. In addition, asymptotic outage analysis at either large maximum transmit power or large maximum interference power is proposed to have useful insights into performance limits of underlay cooperative cognitive networks. Analytical results reveal that underlay cooperative cognitive networks dramatically suffer outage saturation phenomenon, and saturation degree significantly depends on channel estimation quality. Moreover, the performance of both licenced network in terms of interference probability and unlicenced network in terms of outage probability is considerably deteriorated by channel estimation error. Furthermore, optimum relay position is dependent of several factors such as maximum transmit power, maximum interference power, licensee position and channel estimation quality.