emacs ( recompile -y )

Here's some code to solve your first problem (interrupting the current compilation):

(defun interrupt-and-recompile ()
  "Interrupt old compilation, if any, and recompile."
  (interactive)
  (ignore-errors (kill-compilation))
  (recompile))

For your second problem (scrolling the compilation output), just customize the user setting compilation-scroll-output.

This behaviour is governed by the compilation-always-kill global variable. Customize it via customize-variable and set it to t.

Not sure which version of emacs first had this, but 26 and newer certainly does.

I somehow need to put kill-compilation into a ignore-errors with Emacs 23.2 to get it to work when no process is running. Otherwise works great.

(defun interrupt-and-recompile ()
  "Interrupt old compilation, if any, and recompile."
  (interactive)
  (ignore-errors
    (kill-compilation))
  (recompile)
)