Tried all ....but still not been able to transfer my old iphone xs data to iphone 12 pro......any suggestions ?

Not sure of problem. Here are the various Apple documents on transferring data for review.

Transfer data from your previous iOS device to your new iPhone, iPad, or iPod touch - Apple Support

Use Quick Start to transfer data to a new iPhone, iPad, or iPod touch - Apple Support

Use iCloud to transfer data from your previous iOS device to your new iPhone, iPad, or iPod touch - Apple Support

Use iTunes or the Finder to transfer data from your previous iOS device to your new iPhone, iPad, or iPod touch - Apple Support

Have you tried to back up the XS and load the 12 from that? There is also feature that allows you to wirelessly transfer your data from another device using a visual code, have you tried using that?