Learn English – What’s the difference between “at least [number]” and “[number] or more”

You could say, "Pick a number from one to ten". This is usually understood to be inclusive - going from A to Z doesn't mean you start at B and end at Y, and working from Monday to Friday doesn't mean working only three days a week. Or, if you want to be extremely precise, say "Pick a number from one to ten, inclusive".

When I was in Elementary school, our teacher taught us more in relationship to "greater" and "greatest".

You use "greater" to compare two people:

Janus is greater than Mike.

but if you're comparing to a lot of people you use "greatest":

Janus is the greatest [person I know].

In this case "more likely" relates to greater while "most likely" relates to greatest.

Because "more" is used when comparing two people, you would say:

Janus is more likely to commit crime than Mike because Janus has a history of mania.

However, if you wanted to use "most likely" you would say:

Janus is most likely [in the group] to commit crime because Janus has a history of mania.

An easy way to remember is more ends with the "er" sound like "greater" and most ends with "st" just like "greatest". (It's caused a few spelling mistakes for me in the past, but it helped me to remember which one I wanted to use on tests).