Is it possible to play on an moblie emulator, and get a timed run?

Did you read the rules? "The accepted emulator for the GBA games is currently mGBA (only via the standalone client). All other emulators are banned." So feel free to do runs but you cannot submit any of them unless you are using mGBA.

You can play on mobile, but you can't speedrun on mobile emulator

A more direct answer: You are free to attempt to speedrun on a mobile emulator to your hearts content (I got my start on a calculator, fun story). HOWEVER, we will not accept a run to the leaderboard that is ran on an unapproved emulator.

You can speedrun on mobile as long as your using mGBA and run BIOS