Can I replace 27.5x2.25 tire with a hybrid/road tire?
Yes, you can replace your 27.5 tires with 650b tires as long as they fit your current rim. You need to get the internal rim width (B on the next picture) and use the following table to see if you can use the tire that you want on that specific rim. As long as the combination of internal width (in mm) and tire section width (in mm as well), then you should be able to use a narrower tire. Keep in mind that the table is fairly conservative, but when it comes to safety, it's always better to do things properly to avoid personal injury.