Federalists did not "support" the British in the War of 1812. There is a big difference between supporting the British and opposing a war entered into without preparation. What was left of the party opposed getting into the war.
There is so little difference between the Democrat-Republican party and its descendant, the Democrat Party, that it is not worth speaking of.
Federalists in New England wanted to secede from the Union and that's the reason they don't exist anymore. I'm no fan of either of the two 1800's parties, but the Democratic Party we know today was founded by Andrew Jackson and Martin Van Buren during the 1820's. The Democrats are liars when they say that they're the party of Thomas Jefferson.