iPhone 5 After Switch Off Won't Power On/Charge

[asilaydying2012]

iPhone 5 After Switch Off Won't Power On/Charge but iTunes detected in Recovery Mode and able to Restore back to Normal working iPhone again (iPhone Never Been Repaired/Replaced)

- using 3rd party Charger & Cable

1st Scenario: iPhone suddenly died then after PowerOn Stuck On Boot Apple Logo then Restart Loop with Altenate Color Display: Blue, Green, Red

- First Attempt Repair: Restore then back to Normal again then suddenly died again then back to 1st Scenario but still iTunes can detect it in Recovery Mode then able to Restore back to Normal Again

- haven't tried replacing Battery coz i'm able to use it in Normal Mode again

2nd Scenario: (iPhone Dropped) then after few weeks suddenly died then this time won't power on but iTunes Detected then after Restore back to Normal again(Charging/iTunes = OK) but this time when manually switch off it wont power on but still iTunes can detect it in Recovery Mode then able to Restore back to Normal Again

Question:
1. What are the possible cause?
2. Need for Battery replacement?
3. Need Charging Port Problem?
4. U2 IC was damaged and need replacement?

Any ideas?..please help