SRS stands for "Sounding reference signal". it is configured by eNodeB for an UE to measure and report channel condition across the spectrum so that eNodeB can take this as input while allocating radio resource across the system. SRS is transmitted inlast symbol of sub frame(configured). Whereas CQI stands for "Channel quality indication" which is reported by UE to eNodeB. It might be periodic or aperiodic. Based on the CQI report from UE, eNodeB uses relevant MCS (Modulation and Coding Scheme for the better possibility of decoding.
For DMRS looking for other's response since I am not much aware.
