2. unwanted R sound
core and more: they can have r at end /ccr/ /mcr/ with c as its mirror image.
4. can and can't
If 'can" is at end of sentence or before a pause, a should pronounce as /ae/ 強讀
I can't swim. /ken/ or /ken/ with /e/ upsidedown
弱讀 in the middle of sentence unless you purposely stress it
Yes, you can. /kaen/ 強讀
If I can, I will go. /kaen/ 強讀