I haven't read the full thread so apologies if I am repeating things said by others.
Renting to get a school place is clearly in breach of the rules.
If you rent whilst owning another property most LAs will use the address of the property you own and ignore the property you rent.
Those LAs that have a problem generally have a blacklist of addresses that have previously been used by people renting in order to get a place at their preferred school. Any application from those addresses will be looked at with suspicion.
People do get caught, both through the checks run by councils as part of the admissions process and through other parents alerting councils to families renting to get school places.
Many people who try renting for a place are caught during the admissions process but never realise they were caught. In this situation the council will use the correct address for the application (i.e the families actual address, not the rented property), so the child will still get a place. It sometimes happens that the family still get a place at their preferred school using the correct address, so renting was pointless. However, as they are unaware of this they will tell people that they beat the system through renting.
If you are caught after offers have been made you are in a worse position. The offer can be withdrawn even after your child has started at school. Your child would then end up at whatever school has places available, which is likely to be an unpopular school which could be a long way from home.
The number of parents caught renting to get places is rising every year. I am sure some people get away with it. But you are cheating and taking a huge risk if you rent just to get a school place.