How to reset to factory after using littlefoot app?

I have tried the “hold mode button, then briefly press power button” or hold them both for a long long time.

But my Lightpad block M will load my own app (which overrides the mode button, not sure if this is the cause), and then BLOCKS dashboard and noise app and roli play all didn’t detect my block anymore.

If you connect your Lightpad to BLOCKS dashboard and load a different script such as the Note Grid it should overwrite your littlefoot app from the Lightpad internal memory. Sometimes it does take a couple of tries to flush the memory.

EDIT: You can also try a software reset in the dashboard from the Blocks > Reset Application Settings menu item.

True, and seems really Ned to try a few times to be successful.

And can I ask what could I do to write my own Littlefoot app and interact with iOS noise App ?

Say I downloaded a sequencer Littlefoot program from github, can it interact with Noise ? Is there any rules or guidelines for self written Littlefoot script to be able to interact with iOS noise ?

After all, the custom script sends midi for Noise to play the sound. But seems Noise rejected the blocks connection for an unknown reason

If your LittleFoot program sends the right MIDI messages to Noise it should technically be sufficient to work. You can also have a look at the default scripts included in Blocks Dashboard as these are used on the Block to send MIDI messages to Noise.