You're quite right Bernard re switching jacks - there is a provision to use an external stereo mic with a 3.5mm jack. This is a switching jack which disconnects the fitted mics. The XLR mics (or other signal sources)would be in addition to the fitted ones.

You can record single tracks in four track mode but the handbook is not the asiest to follow

Our use for the H4s that we have is as a simple good quality portable recorder. For this it is simple and convenient and produces excellent quality in either MP3 or WAV formats.

Stu