Albina in the chorus is drowned out by the backing vocal track, and because that is essential her own voice layered, it gives the impression that she's just lip-syncing. But it's clear from the "oh nooooooooos" especially that she is singing live as well. Same goes for Azerbaijan, the layered backing vocals of Efendi's part are giving her the opportunity to perhaps not give her all at those sections. But it may just be that during these rehearsals, they see no need to give 100% in terms of live vocals all the time and the clips we are seeing are simply showing sections when they were holding back.
Moldova is definitely live, because I remember being underwhelmed by her live vocal, and the fact that she looked and sounded a bit perplexed and bored in the 1st rehearsal. Again, big notes, she won't always go for them in rehearsals - it doesn't mean that she's going to go for the lazy route in the jury show or the actual semi final.
Killing your voice by singing high notes over and over again, especially considering the amount of run-throughs and rehearsals they would have before the actual judged shows wouldn't be recommended at all.