Solar charger for Lipo battery
Is it enough to hook the lipo battery to the charger?


ANS.: What do you mean? According to me, it is quiet enough, only if the setup is for charging the battery only. 


  Its needed a diode at Vin pin?


ANS.: I don't think so. Why would the pin need a diode? It is of no use as the solar panels would never provide reverse current. Moreover, these diodes have at least a resistance of 5 to 10 ohms. This will reduce your input current. Do not add a diode.


  Supposing a constant value of light (ie. in the case the cells are providing the 120mA) how much time it does take to charge a 2000mA?


ANS.: I guess you mean "2000mAh". Supposing the cells provide 120mA current, and due to internal resistance of the charger, the output current is 100mA, then the time taken to charge the battery would be 2000mAh/100mA = it would take 10 hours to completely charge the battery.


  Its worth to attach at the output of the charger a boost converter (based on AOD4184,SD1040CS and LTC1871 ), so it can be charged at least two battery on parallel?


ANS.: Yes you could do that.