Easiest:
A Song for xx
HANABI
HEAVEN
evolution <--
About You <-- the key to evolution & About You is just to know the lyrics
walking proud
CAROLS
HAPPY ENDING
Heartplace
Over
Dolls
is this LOVE?
forgiveness

Hardest:
TO BE <-- I need to be realllly warm to make the jump in the chorus
Moments <-- One of my favorites, but it's just in an awkward key for me
still alone <-- My voice gets so exhausted by the end! Really need to warm up
M <-- Not sure why, but I just never like the way I sound on this song.
ourselves <-- I know them all, but I always get the choruses & the "-tari" parts mixed up