If you do this, you'll run in to kernel management complexity. It's much easier to try the live version or try the later version in a VM.

If you really MUST have them both installed, I'ld install them on separate disks with grub installs to mbr on both. Then you can specify which disk each os_prober should search with an edit like this.

Finally, you can choose which disk to boot at your bios screen.

It keeps the whole process dead simple.