We observed sixteen 1.3 mm sources in the Serpens Main star forming cluster in the CO and C18O J=2-1 lines as well as in 1.3 mm continuum at an angular resolution of 0.5" (220 au) using ALMA in Cycle 3. These sources are classified into three groups: (1) six sources with extended (>1000 au) continuum and CO outflows, (2) four extended sources without associated CO emission, and (3) six point-like sources with compact CO outflows. The Group 1 members are considered to be typical Class 0 protostars from their SEDs (Tbol<60 K and Lbol/Lsubmm<15) and monopolar/bipolar outflows. They also support evolutionary trends predicted by theoretical studies, such as outflow widening, CO desorption, and disk growth. In particular, SMM4A in Group 1 has the largest disk (r~240 au) and the widest outflow among the Group 1 members. The Group 2 members are embedded in a natal filamentary structure. They have lower densities (<~10^8 cm^-3) than the Group 1 members. The densities indicate that the Group 2 members are marginally Jeans-unstable. These results suggest that Group 2 is prestellar cores. C18O emission is clearly detected only in the member having the highest density in Group 2. This is also consistent with the picture of prestellar cores. The Group 3 members have their counterparts in near infrared, including Class 0 and I sources. They also have less massive envelope (<0.05 Msun) and less clear CO outflows than the Group 1 members. These results suggest that envelopes are dissipated around the Group 3 members. Because of envelope dissipation, disks, if any, around the Group 3 members will not grow up anymore from the current size, HWHM<60 au. Sizes of protostellar disks range from <60 au to ~240 au in the same star forming cluster Serpens Main. This diversity in disk size can been seen even among Class 0 sources in this region. These results may imply diversity of protostellar evolution in a protostellar phase as early as the Class 0 phase. Such different types of protostellar evolution could be an origin of disk-size diversity in the T Tauri phase reported in recent ALMA surveys.