How to know whether the issue with your smartphone related to H/W or S/W?

If these things happen it should be considered a Hardware issue or fault:

• Battery:{ You can notice swollen battery or back surface of your smartphone. }{Your smartphone gets switched off within minutes of turning it on and doesn’t wake up at all even after repeated reboots.}{ Battery life is consistently very low.}[Time to replace battery by visiting service center]
• Screen:{ You just see the display as if it’s a calculator display[issue with backlight] . }{You see light bleeding from edges of the screen.}{ You see cracks that are deeper and the display doesn’t respond to touch. }{Your screen doesn’t have any visible scratch or cracks but ghost touch and opens some random app without even touching the screen[happens due to drop]}
• Speaker:{Doesn’t produce sound at all}{Says headphone jack is inserted even when it is not[Water damage or dust accumulation in 3.5mm jack]}{Sound from speaker is heavily distorted.}
• Earpiece and Microphone:{Person on the other end of the call can’t hear your voice at all}{You can’t hear the voice of caller if you do not keep it on speaker or use earphones}
• Power and Volume buttons:{No response till you press very hard}{No response at all}{One of the buttons doesn’t work}
• Camera:{You can easily notice cracks or broken glass or plastic above camera}{Camera view finder isn’t visible even when tried with non-stock camera app}
• Processor or motherboard:{Water damage or Extreme overheating or Hard drops leading to dead phone[Not worth repairing]}

If these things happen it should be considered a Software issue or bug:

• After applying latest update you started experiencing variety of problems in battery life, standby drain, frequent reboots, freezing apps, laggy UI, poor performance. [Solution: If possible downgrade to previous version by manually install or wait for the next update]
• Camera not detected warning or camera crashes in-between during shots.
• Device over heats during gaming but not by a huge margin above normal levels.
• Recent app you installed is to be blamed if you see variety of issues like lags, pop-up ads, battery drain or auto wake-up. Uninstall the recently installed apps.
• If nothing fixes software issues. Factory reset your phone and remove all the junk apps.
• Reset settings to default. Take backup to HDD or laptop. When you notice small issues related to S/W.

Thank you. Hope it helps.