Is it allow? download and run lua script

to fix bugs

How does the fix works ? Changes code ? That would not work.

Is it an iOS or MacOS App ?

For MacOS, check guideline 2.4.5

2.4.5 Apps distributed via the Mac App Store have some additional requirements to keep in mind:

• (ii) They must be packaged and submitted using technologies provided in Xcode; no third-party installers allowed. They must also be self-contained, single app installation bundles and cannot install code or resources in shared locations.
• (iii) They may not auto-launch or have other code run automatically at startup or login without consent nor spawn processes that continue to run without consent after a user has quit the app. They should not automatically add their icons to the Dock or leave shortcuts on the user desktop.
• (iv) They may not download or install standalone apps, kexts, additional code, or resources to add functionality or significantly change the app from what we see during the review process.

Check also: 2.5.2 Apps should be self-contained in their bundles, and may not read or write data outside the designated container area, nor may they download, install, or execute code which introduces or changes features or functionality of the app, including other apps.