Precautions and bugs of board

here precautions should take while using arduino plugging long 5 hrs. , uploading multiple sketches 1 one without removing other wirings pin header okay or not because while doing observe sketches digital serial read blink , fade these stopped working on board , whenever connect breadboard circuit doesn't work when unplugged arduino , uploaded program , rewired circuit 3 work fine reason please tell

i try reading once put punctuation required in english.

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Arduino Forum > Using Arduino > Project Guidance > Precautions and bugs of board

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