Can I use the mysqlhotcopy backup files to different machine which different MySQL version?
if it's within same minor number of mysql (ie, 5.1.12 and 5.1.24 should be fine, but not 5.2.1) - should work without problems.
if you are going from older to newer version - should work without problems.
for both cases - run
to be on the safe side - preferably set up virtual machine with same version of mysql as source host, restore your backup there. run proper mysqldump and import the date on the destination machine.