DS1 hated tummy time, he started comano crawling at 10 months and proper at 13 or 14 months, walked at 21 months.

DS2 hates tummy time so much so when I put him down on tummy he is flipped over before i have stood straight up again!! He wants to sit up all the time and will happily sit up for ages. He has been rolling both ways from 4 months but very rarely rolls onto tummy.