Select two or more audio files, check the order in the list and remove anything you do not want. Press Merge to render one continuous track, then download it as a WAV.
Yes. Each file is scheduled into a single offline rendering context, and the browser's resampler converts every clip to the highest sample rate found among your files, so mismatched inputs still line up correctly.
There is no fixed limit, but everything is held in memory as raw audio, so very long combined tracks can run out of RAM on low-end devices. Joining a handful of songs or a dozen voice clips is comfortable on most machines.
No. All decoding, joining and WAV writing happens locally with the Web Audio API. Nothing is transmitted, which is why merging works even if you go offline after the page loads.