2. No SQ F lounge access officially. On an award ticket, it would be hard to persuade the matron to make an exception. Give it a try, of course. If you were on a paid F ticket, I think at the slightest hint of irritation at being directed to the J lounge, the SG matron would apologize & welcome you to the F lounge.
3. All SQ J lounges at Changi have showers. Pretty nice too.
4. No SQ J lounge has printers. I was recently annoyed at this fact myself. Free internet galore at Changi.