Single phase refrigeration compressors always have 3 connections - CSR (common, start, run) the first photo shows the compressor has a current relay plugged onto it so you can't see the start pin. Other relays are potential relay and PTC relay. Never centrifugal relay in refrigeration (might have been 50 years ago )
Using a compressor as a vac pump will work but it won't pull down to -30psi like a vac pump will. An R22/R404a compressor or similar will pull down better than a R134a compressor because they are more heavy duty with higher head pressures on those refrigerants.
Edit: looking at the 1st photo again it might be a PTC relay.
Using a compressor as a vac pump will work but it won't pull down to -30psi like a vac pump will. An R22/R404a compressor or similar will pull down better than a R134a compressor because they are more heavy duty with higher head pressures on those refrigerants.
Edit: looking at the 1st photo again it might be a PTC relay.