Dear Pulkit Khurana,
Thank you for posting in Microsoft Community.
I'm sorry that Icons tab is missing in your PowerPoint. I'd like to help you, we can work together to narrow down the situation and move towards a resolution path.
You mentioned it's not even present in illustrations in file options.
May I know if you go to File>Options>Customize Ribbon>Choose command from All Commands, can you find the command "Insert Icons", as shown below?
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If you don't have the Insert Icons command, you may also try following steps to insert icons:
From Insert tab, click Pictures, choose Stock Images from the drop down options, from the pop-up window, see if you can find Icons tab, as shown below.
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If you still cannot insert icons in PowerPoint, you may try Online Repair Office.
For more detailed steps, please refer to this support article Repair an Office application
If same issue persists, I understand how frustrating this situation can be and sincerely apologize for the inconvenience caused. Let me help you further. I would appreciate if you could share following information:
1.Could you please share a screenshot of the Insert tab in your PowerPoint?
2.May I know the version and channel of your PowerPoint App? Please go to File>Account, then capture a full screenshot of Product Information from the Account page.
We look forward to hearing from you; Please understand that our initial reply may not always immediately resolve the issue. However, with your help and more detailed information, we can work together to find a solution.
Thanks for your cooperation and understanding. I hope that you are keeping safe and well!
Sincerely,
Tina | Microsoft Community Moderator