Can I just wear the denture over the healing caps without having abutmentss?

Yes you can, this is a very normal way to perform implants , this is called the 2 stage proceedure, you do not load implants on the first surgical proceedure, thats why you have healing caps, just aloud the doctor to make space on your denture for healing caps, the best way to go, is not to have the healing caps, to be loaded, and after 3 months, now, you will be ready to receive the abutments, unless you had the ALL ON4, FROM NOBEL BIOCARE, this is the only technique and protocol, that alouds, you to have immediate load.this is a very common procedure with implants and dentures.

Well, you can but you won't get the full benefit of the implants. Furthermore, the healing caps will eventually unscrew and fall out. You could lose them and the gums will grow over the implants further necessitating another minor surgery to uncover the implants and more costs for new healing caps. It's not the way to go and your should reconsider and get your implant restored properly. 

You can´t. without abutment your teeths will not have a retention. Healing caps are not tightened. Implants are supposed to be permanent and thats why it can´t be possible. If you want to have your teeths receiving their benefits, just wear your abutments.Good luck!