cutting torch would be easy way. Could try some PB Blaster may work if you keep soaking them.
Hit it with a hammer
Hacksaw
A cutting torch is one answer.
Put in Hot water
A magnet
a large hammer
Rusting bolts normally indicates that the bolts are brittle. Taking a pair of water pump pliers and squeezing really hard will most of the time break the rusted bolt so you can remove the toilet seat. Otherwise depending on the type of toilet seat installed, you can drill a hole right through exactly where the rusted bolts slot in, so helping you remove the toilet seat.
Lug nuts are still on, wheel is rusted to the hub.
Your going to need to get a special puller if its rusted on, usually if its new or not rusty you can just remove the bolt and hit it with a hammer a few times and it will come right off but if it is rusted then you should get a crankshaft dampner puller
You can try spraying the rusted parts with a penetrating oil like wd40 or a product designed to loosen rusted on bolts. Let it soak for a bit before trying to remove. In my experience a big hammer is big help.
Most rust can be removed by a steel brush if its not to rusted
probally if not to bad rusted with a wire brush if really bad rusted use a wire brush hand grinder wheel that is what helps me in when i have to weld rusty metal