how to change passcode on ipad without the device

Hello,

Are you asking how to change iPad’s passcode remotely? This is not possible.

Read this information. If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

Hello,

If Find My iPad was enabled and the iPad is currently connected to the internet then you can remotely lock the iPad from iCloud.com. If not then no there is nothing you can do.

I don't think that is going to be possible rightnow or forever! If you can do that, then it will be easier for hackers :P

unless if your device is stolen, you can just go to findmyiphone ans del all the info. (Hope you backup all files in your cloud !)

goodluck :)