I got a Raspberry Pi 3 Model A+. I immediately inserted an sd card and booted it up it went well for one day and then after an update, I could not reboot it up so then I formatted the sd card and installed noobs in it again. but this time some of the apps didn't start like sonic pi, sense hat emulator and chromium. After much trying I finally thought of reinstalling the os and This time I thought of dual booting it with Raspbian and LibreELEC_RPi2. So now both the os didn't work. I thought this could be an issue with the power supply because in the instructions it was written 5V and 2.5A(min), and I was using a charger of 2.4A. After that, I checked the rating of the original RPI power supply, which was 3A, so I got a charger of the same rating.
After I plugged it in the socket there was some fluctuation in the main power supply and now only PWR led lights up and not ACT led. I tried formatting the card again, even bought a new sd card reader, I even tried booting with a pen drive.
Please tell me what to do as I am a beginner in this.