20 month old very picky eater

[Glitterypinksam]

Hey there all, this is my first post on here so apologies if it is an essay hahaha!
Up until about 15 months my 20 month old daughter was a fairly good eater. When I say this I mean she would eat most things in a puréed but lumpy texture. We then had about 3 months of not eating anything but baby cheese puff crisps. Then all of a sudden she started eating baby microwave meals as well as homemade meals. She is slowly attempting to feed herself with a spoon but I still feed her to make sure she eats more, she doesn't ever finish a bowl though. This is followed by yoghurt.
Other than this she won't eat any other type of table food, apart from, toast, cereal, popcorn, yoghurt coated dried fruits, baby crackers, yoghurt, chocolate (very rarely give it to her) and biscuits again these are limited.
I have tried everything, I put a couple of pieces of food to try on her tray but if it's anything she doesn't normally eat then she throws it across the room. I've persevered with picking it up for days, I put it by her mouth and she won't even open her mouth to try it. I have tried hundreds of different foods but she just won't have them. Even finger sandwiches get thrown.
She goes to nursery half a day a week, and she doesn't eat there either she will just go without. She still has milk (when she wakes up with her breakfast, for her afternoon nap, sometimes mid morning and mid afternoon, but if not then just to go to bed on). I have tried the taking her dinner away if she won't eat but she wakes up in the night wanting milk cause she is hungry. She will have fruits/veg puréed in the baby pouch.
I'm really starting to worry now because (I know we shouldn't compare children, and in don't usually, but on this I am starting to do this) lots of children I see her age are eating such a variety, I would be over the moon if I could just get her to eat a little more variety but she won't even try let alone eat them. I've have tried disguising fruit in yoghurt etc but she just picks it out her mouth. She will steal my apple and chew the pieces she bites off then throws them on the floor.
Please help.........swiftly pulling more of my hair out.
Sam x