@Tony *********
yes a multi entry visa requires you to leave and reenter.
Almost everyone takes the single entry.
Otherwise you have to leave and return to keep your visa/stamp alive.
There are specific reasons some choose a multi entry visa.
Yes Non-O visas can be multi-entry in most cases not what you want.
If you want to be able to enter and exit on a longterm visa/extension a few times a year, you need a reentry permit NOT the visa.