Alright, for testing purposes, I guess you should be concerned with the location of the fracture. For real world purposes, you will have no idea if there is a fracture, or where it is located...all you will know is signs of neurological deficit, and treat the treatable.
Immobilizing an infant is done the same as an adult, with an appropriate sized c collar, and the addition of a roll under the shoulders to assist in maintaining an open airway. I guess if you for some reason did not have a collar in the correct size, then you do the best with what you have...a towel roll could be used, but it is not ideal.
Splinting for dislocations is same as fractures, as the earlier poster mentioned. Assess PMS first, splint appropriatey, assess PMS again, and then basically continuously assess PMS, and make sure you document it. Who knows how far down the line someone may lose PMS in an extremity, and the blame may come back to you if you did not chart well. Pain management as allowed in your protocol is important also.
That is interesting about the knee dislocation. I have never heard that about field reduction specific only to knee injuries. The old protocols I used to work under had a provision for one attempted field reduction, if PMS was not intact distal to the injury. After one attempt, no more manipulation was allowed without further orders. Protocols are like snowflakes though, no two are ever the same, and some doctors make changes and additions frequently to keep up with the trends...