Hi Pranav,
Please try this policies registry fix to resolve the issue. Download and run the REG file. Click Yes to confirm.
Reference:
Startup Apps Option Missing in Settings in Windows 10 or 11:
https://www.winhelponline.com/blog/startup-apps-option-missing-settings/
Hopefully, it should bring back the "Startup" option under "Apps".
Additionally, if you'd like to have a thorough checkup for malware, do the following:
- Download Farbar Recovery Scan Tool (FRST64.exe) [See also: Collect Farbar Recovery Scan Tool logs.]
- Rename FRST64.exe to EnglishFRST64.exe.
- Run the program. Don't check or uncheck any options. Click "Scan".
- Upload the two logs, FRST.txt and Addition.txt, to your OneDrive and share the link here.
(How-To: Share OneDrive files and folders - Microsoft Support)