At least it seems he's not even remotely a romantic rival anymore. He seems to like Hera, Hera likes him. Bingo bango bongo, go get married and leave the lesbians alone.
And at least our main couple (well, Xiao Yang at least) is ok with helping them pair up towards that.
Unlike the other useless lesbians couple
On the answer...
A is the least plot-impacting option but will also hide their relation so I don't think this is the one.
B is frankly something I hope for but the description is too vague so probably no either.
C is the most realistic option. The 'incognito' mask theme implies even if you noticed it's someone, you're not supposed to call their identity out.
So anyone who can read the line should understand that prince like hera (dancing with her) but this isn't him siding with old noble (mask = everyone's status doesn't matter)