[wlug] oldest usable Android version -- any opinions?

Apologies for straying off topic. I need to get an Android phone to replace an ancient Sony-E, but hanker somewhat for the days of removable batteries, and like a stylus. This points afaict to an older Samsung Note model but then comes the problem of obsolete versions of Android. Can anyone suggest what is the oldest Android that can still be used on the web of today? Or perhaps there is a current phone with removable battery? ~ Ian Y