At between 0:30 and 0:44 of the video, my rough transcription:

Questioner: Are you going to make sure that people with preexisting conditions are covered?
Donald Dump: YES

also,

Donald Dump: I will not cut Social Security unlike every other Republican, and I will not cut Medicare or Medicaid

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As for Medicare, there are a number of provisions in the ACA like closing the prescription drug donut hole and also various free screening procedures that would go away if the ACA is fully repealed.

As for Medicaid, the 90% federal funding of the expansion part goes away (along with the expansion part of course)

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For those who might be wanting to know "The real reason the GOP wants to kill Obamacare" -- that comes in the last half -- the ACA was paid for partly by taxes on high income (top 2 brackets) people -- the 0.9% Medicaid surcharge on earned income and the 3.8% Net Investment Income Tax (NIIT) on unearned income. Anyway, those taxes on the top 2 brackets would go away with total repeal of the ACA.

Robert Reich doesn't talk about those taxes specifically, but he does talk about the average tax cut that the top 1%, the top 0.1%, and the top 400 households will get