Is it possible to use front 110/70 R17 & rear 150/60 R17 on my CBR 250R bike?

It is recommended to go to an authorized service center to get the 150/60 tyre installed at the rear of your Honda CBR250R. The 140/70 tyres are the standard size for this model and should be kept as such. The service center should be able to provide more information and answer any other questions you may have in regards to this issue.