One at a time:
a) ball is on the fringe and I plan to use my putter.
Rules don't care what club you might want to use
b) In my line, on the fringe, is some sand, a pebble and an acorn.
On the fringe - cannot move the sand, may move the pebble and the acorn which are loose impediments
c) On the green, in my intended line, I have a ball mark and what is most likely a spike mark
On the putting green - may repair the ball mark, may not...