Hi @Krish-1, do I understand you correctly in that you have deactivated an app and wish to activate it again? You may do so by going to Settings > Apps > find the specific app you wish to activate > Activate.
Regarding the photos, have you deactivated the Album app or in which way are you not able to access the photos in your photo Album?
I apologize if I misunderstood, but if so, please provide some more details and I'll be happy to assist you! 
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