A multistatic cloud radar system is investigated, where receive antennas (RAs), or sensors, communicate with a fusion center (FC) over a multiple-access wireless backhaul. Each RA receives a measurement of the signal sent by a transmit antenna (TA) and reflected from target, possibly in the presence of clutter and interference, amplifies it, and forwards it to the FC on a wireless fading channel. The FC receives the signals transmitted by the RAs and determines the presence of a target. The problem of maximizing the Bhattacharyya distance as the detection performance metric under power constraints for the TA and RAs is formulated with respect to the transmitted code vector and the gains applied at the RAs. A short-term adaptive design is first considered that leverages the instant gain of the RAs-to-FC channels, and then a long-term adaptive design is considered that uses only stochastic channel state information (CSI). Algorithmic solutions for both scenarios are proposed based on successive convex approximation, and the performance is evaluated via numerical results.