Can you download mods for minecraft on your iPhone?

Yes you can, but it is very hard to do.

Yes you can install mods for minecraft on your iPhone, Download and install BlockLauncher. This is a free app that manages mod files for Minecraft PE. It is one of the only reliable ways to install mods on the Pocket Edition of Minecraft. Another possible launcher app is PocketTool, which uses mostly the same process. But If you are a smartphone user, do install Leo Privacy Guard app.