The Star of Temasek has never been awarded. Neither have the
next two medals. Therefore, the protocol toward their bearers has
not yet been fully established.
I suspect that even if it were not required, the current President
would be happy to salute a bearer of the Star. President Nathan is
a very humble man in person. He even has standing orders for guests
not to rise when he enters as a guest of honour. I am happy to say
that starting from Wee Kim Wee, all our presidents have been
excellent chaps.
As for the Prime Minister saluting the bearer, that's a different
story. However, given that the PM is a former general, and
apparently a very caring one toward his men based on personal
accounts, I suspect he would also be happy to salute a bearer of
the Star. It would be good for morale in any case. SM would also
probably be quite OK with saluting. He is not overly concerned with
rank and is a nice guy. MM -- totally different story. Nobody can
safely predict his actions. 
The Medal of Valor has been awarded several times. I think it is
the lowest military award for gallantry. The famous COL Lo Yong Poh
got one for running around Kabul unarmed negotiating peace between
the warlords for the UN, while the city was being heavily shelled
by said warlords. Dodged a lot of shrapnel for peace. A few were
given to the SOF troopers who resolved the SQ hijacking. A few were
given for bravery during the NZ artillery accident, to the
surviving gunners who got their injured and dead mates away from
the gun and made safe the remaining ammunition -- despite the fact
that they were themselves missing limbs or eyes in some cases.
Seriously tough -- and they were just NS boys. I think a NZ Army
SGT also got the medal in the same incident. There are a few others
which I can't remember.
I think that the Medal of Valor is also the highest award given out
so far, so MINDEF has high standards. That is a good thing.