Nope, only applies to people who are applying for a new visa from consulates outside the US. Does not apply to people who already have visas or who are applying for adjustment/change of status from within the US.

no but if your stay is above 6 months, you become a candidate for admission and will therefore become subject to inspections under all grounds of inadmissibility, including Public Charge. If you are a recipient of federally funded benefit including medicaid, you might be deemed inadmissible.