On the SP-404 / SP-303, can I change the length of a sample while maintaining the original pitch?

Are the pads on the SP-404 / SP-303 velocity-sensitive?

On the SP-404 / SP-303, I'd like to change the BPM of a sample while maintaining the original pitch. How much can I stretch or compress the sample length?

Is there data compatibility between the SP-303, SP-404, and SP-606?

When I change the tempo of a pattern on the SP-404 / SP-303, the sample playback remains unchanged. How can I get my samples to follow the tempo change?