Reine,
You are correct on E. buruana. I am a little mixed up. I purchased E. pseudocactus but was out and they gave me E. buruana instead. I knew they grew a caudeces only from seedlings, but from stem cuttings, a swollen root. I did own one in the past but gave it away to some one who loved it.
The I.D.'s on last picture;
1st. on left; Euphorbia Crown of Thorns variegata.
2nd. from left; Euphorbia lactea variegated 'Ghost' gift from Hetty.
3rd. in middle; Euphorbia Red Trigona Tree.
4th. on right; Euphorbia lactea variegated 'Ghost' from stem cutting off E. lactea crestata.
Stush