Hey @Mark, welcome to the forum, for the last question:
- Elive should include correctly the bootloaders of other OS systems, if you run the command "sudo os-prober" you should see them listed (this is the tool which should detect these systems), if they are not, the cause of the issue starts here
About upgrading the distro, the short answer is: elive takes care to upgrade itself in the most compatible way so you should not worry for that, but is recommended from time to time to do a newer installation (with the upgrade mode, not a clean install) which will not only clean the system but especially will provide extra features that may be not included in the upgrade, more information of these details can be found here: How to update your Elive, the correct way