Hi, how old does my baby need to be to sleep with a blanket? She’s 14 months, sleeps in her cot with just a comforter and a sleep suit.... Also how old to sleep with a pillow

Most toddlers are unlikely to stay under blankets while in a cot.
If you are concerned about your child being cold, then an extra layer of clothing can be worn under the sleep suit/bag, rather than loose blanket or doona.

Red Nose has the following information about the use of pillows & soft/loose bedding.

Soft bedding is dangerous in a cot and should not be used. Soft bedding includes pillows, quilts, doonas, soft toys and bumpers. Soft bedding may cover the baby’s face and obstruct breathing and/or cause overheating.
Older babies in a cot can be at an increased risk of a sleeping accident by using pillows and bumpers as a step to climb up and fall out of the cot. It is safer to wait until the child starts to sleep in a bed before introducing a pillow or other soft bedding.
https://rednose.org.au/article/at-what-age-can-i-introduce-cot-bumpers-and-pillows

Red Nose does not recommend placing a pillow where baby sleeps unobserved. It is safer to wait until the child starts to sleep in a bed before introducing a pillow. The Australian government states it is safer not to use a pillow at all for children under two
https://rednose.org.au/article/pillow-use