Which would you say are the 5 (or more.?) most useful general asanas to know and use.?
for myself i like.
Tree
sun salutation
Shavasana
downward dog
Matsyendrasana.
I benefit most from:
Chakrasana (wheel pose)
Kandharasana (Shoulder pose)
Merudandasana (spinal column pose)
Gupta Padmasana (hidden lotus pose)
Utthita Hasta Padangusthasana (raised hand to big toe pose)
I like to more or less always include these one in my private practice.
There are a few other variations which I don’t know the names for, which I also like, but too lenghty to describe them here.
Foreword Bends (standing, seated, wide ect.)
Cobra
One Legged Royal Pigeon
Lotus
and of course Corpse 
tadasana
savasana
bujhangasana if you can get into it. (I can’t, very well)- i don’t think this is that important than some of the others but a mild backbend expressed through one of the asanas( as well as amild gentle twist) is useful.if you can get it ,gd.
sirsasana.
virahabradasana ( sounds a bit like viagra does’nt it?)
lunges, i do like- kneeling or standing
mild down-dogs
trikonasana is probably one of my favourite as well as the standing lunge/warrior**(arms above the head) - i reaaly struggle with the former,somewhat better at the latter. i like all the variations too.
the sun salutation covers the all the core ones, though.
my mind’s just gone blank there…
Sirsasana
Sarvangasana
Shavasana