Hi @Shanky Tyagi
Welcome to Q&A forum ~
The system requirement for Office LTSC 2021 is the three most recent versions of macOS, not iOS.
The following image is from link: Office LTSC 2021 Suites.
As we focus more on general issues of Office on Windows or macOS machine, if you need further issue of Office on mobile machine, I suggest you post a new thread on Microsoft Answers Community --- Microsoft 365 and Office.
Thanks for your understandings.
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