LP and LK dont always combo into headbutt or shoulder.
What character do these combo on?
all of them afaik, depends on distance and the timing of your cancel mostly.
no, there are a lot of characters who don’t get hit by c.lp/c.lk x lp headbutt. twins, makoto, oro, elena never get hit by it. dudley, hugo, urien get hit by it with the most spatial leniency, and everyone else is somewhere in the middle.
c.lk x lk tackle hits everybody standing as long as you’re as close as possible. when crouching, it doesn’t combo on ryu or ken (but does on akuma) but i think it works on everyone else.