Is there a default/stock sound recorder app? In most of the Android phones sound recorder has a different look and feel and slightly different functionality. So is the sound recorder is a basic feature of all Android phones?
Can I assume that it will be present in all Android phones or is it specially added by manufacturers and there might be a case where it may not present in some phone devices ?
There is no default sound recorder in Android. Some manufacturers add one to their stock ROMs, but the closest thing on a Nexus device is Google Keep, added in 4.3.

If you assume that a voice recording app is present in all Android phones you'll be caught out.