Android Unity 4 Game Upgrade into Unity 6 (All Function need to be work)

I need our current project, built in Unity 4, migrated cleanly to Unity 6 while keeping the game exactly as players know it. The core work is twofold: first, bring every gameplay mechanic over so it runs flawlessly on the newer engine flow on the latest UI toolkit.

No new features are required; this is a straight upgrade focused on compatibility, stability, and a polished feel in the updated environment. I expect you to handle any API changes, package replacements, shader or lighting tweaks, and input-system updates that Unity 6 now enforces. Final delivery is the upgraded Unity 6 project folder ready to open, build, and release version.

In this time run in android, need to work with Windows and WebGL too.