hot - attractive in a way that touches you on a more primal "MUST HAVE SEX WITH YOU NOW!" level. a girl can be hot without being pretty because it comes more from attitude, the way you carry yourself, and your body shape than anything else.
cute - not sure, I don't use this word to describe girls. in fact I don't use the word cute to describe anything other than ingrants or small furry animals. but I think its supposed to mean you're attractive in an innocent and fun kind fo way.
pretty - natural facial beauty. the kind that doesn't need makeup to look beautiful in the face.
Hot usually means someone with a curvaceous or tight body ie. one that causes everyone in the room to turn their heads
Pretty usually means someone with a very beautiful or elegant face, body, demeanour or dress sense
Cute means someone who looks innocent and acts like a child. In Asia this usually means someone who has rather large eyes, smiles a lot and makes victory signs with their fingers! ^^ Also someone who is cute can also be both pretty and/or beautiful.
Without coming across as a dirty old man I'll use your pics as an example.
Bathroom pic of you in mirror - Hot - as meant to be I presume. Homecoming pic is pretty. The "i love this pic" pic is sexy. the last pic you flagged as an "inappropriate" pic, I thought was cute. So you see, it's all about interpretation. Not all others will agree with my perception of your pics and will say the last pic was hot and the first is just cute. Or in some other order. Each has his/her own taste. To give you a dictionary definition though is almost impossible for me. I'm not that good a typist and it could/would take a while to explain.
Most of what these other people are saying is wrong. Hot means the first reaction to their appearance is felt in your pants, whether due to face, body, or combination of factors. Cute is appealing to the eye and may or may not have pants-appeal; a cute girl, or a puppy. Pretty is usually face-oriented, but is not entirely interchangeable with cute; cute girl, pretty woman.
I think that Cute and pretty are great. Beautiful is super serious, I will only use beautiful if I mean it. Beautiful is a breathe taking thing for me, and it is beautiful inside and out. Hot can be kind of degrading I think because it is very surface level, but cute reminds me of "the girl next door" type, and pretty means good things like cute also.
cute = small girls, pretty = just judging ones face, hot = sexy body / pretty face .. cute is pretty much hot, but they are like 5 inches shorter lol. they are all one in the same pretty much. on a side note, wanna bang?
Hot is a girl that everybody turns their heads to look at when she walks through the door. She's the girl that you definitely would want to sleep with. Cute is being pretty, but not a sexy pretty. More natural beauty and innocent looking than girls who are steaming hot. Pretty girls can both naughty or innocent looking.
To me, hot means, that the person can't resist you because you're so good looking, cute is where you're sort of hot and that the person might like you a little but maybe not at all, and pretty to me is where you just have good bodily features.