file as lowercase does not get syntactically highlighted. File as uppercase does get syntactically highlighted. Also UnvalidatedAssetService does not get syntactically highlighted.
Pretty sure they removed access to File. I think the Local File Importer (Plugin: Local File Importer (Import Images from your Computer!) - #19 by XAXA) plugin used it. That plugin has been broke for a long time last time I checked. Here’s the reference in the post I linked: File - Roblox API Reference.
It does if you put it within GetService()