TG business class food is basically economy class, served on crockery and with metal cutlery. TG has fairly good food in economy, so not all is lost, and you'll get an extra choice of main dish in business class. The meal service takes an hour or two. There's nothing else to do after that except watch movies or sleep. The angled beds are not conducive to sleeping (snoozing maybe).
Theoretically, your star alliance business class boarding pass entitles you to access any star alliance business class lounge. The Melbourne Singapore Airlines 'Silver Kris' lounge however is well known for turning passengers away and directing them to the Air New Zealand lounge. You may need to be prepared to stand your ground and argue your way in. If you can be bothered.
SQ's reason is that they are a 'silver kris' lounge, not a star alliance lounge. You can however be directed to the NZ lounge is the SQ lounge is full or nearing capacity.
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