Can the connection hoses be put over the side of the Intex pool or does it have to connect to the sides? Can it also be used in line with an Intex 28684 Electric Pool Heater?

We wouldn't recommend placing the connection hoses over the sides of the pool and recommend that they should be attached using the connection points attached to the Intex pool. There should be no problem with the filter being used alongside an Intex 28684 pool heater.