I know about 3: there are three effects to gifts. All heal, but 2 out of 3 also provide a bad side effect after some time. The first one is poison. It slowly drains your HP until you die or take an antidote. The other possible side effect is falling asleep. I'm assuming that's what you got when it said "I feel dizzy". What happens if you don't take an antidote is that you fall asleep after some time and is, while sleeping, dragged to the spawn room. When you wake up, the door is locked and Saiko-chan is sitting in the chair, sleeping (she looks cute, try it out). When you pick up the key and unlock the door, she wakes up and starts chasing you.
A note about 5: The shoes don't always spawn in one of the classroom hallways. They also sometimes spawn next to the exit door.