starter motor, fuel pump, alternator, (possibly ECU) and battery need to be attached and wired up properly, be careful and make sure your engine stand can withstand all the vibrations
If the timing is off by a few degrees the engine can start but will run rough. More than a few (depending on the engine) it will not start.
That engine needs fuel, compression and spark to start and run. You are missing one of those.
Change password for the start engine for citroen saxo?
Not unless it is a carburated engine.
Maybe you need to check the oil The oil light will stay on until the engine starts. If the oil light was on when it was running and now it will not start then you may have internal engine damage. Take it to a professional.