Do i check no under were you enrolled in a less common plan and dumb question will the irs know i had medicare health insurance if i do

Medicare (at least Part A, Part C or Medicare Advantage) counts as health insurance coverage. If you had it for the whole year, on the Did you all have health insurance coverage in 2016? screen, answer, "You had health insurance coverage all year".

See the screenshot below.  

For additional information, click on What Counts as Health Insurance for my 2016 Tax Return?