1. Some old stuff does ugly things like writing into unspecified/unused bits of the OCS, these bits were later use to activate features found in ECS/AGA. Results may vary
2. Switching can be done either in early-startup-menu (Kick 2.0 and bigger) or with special SW triggering 1 bit (see 1.) and than reseting the Amiga. Wether your TV will sync down to 50Hz is another question.
3. An ECS-Agnus can address up to 1 or 2MB off chipram (depending on model), but you would need to do some modifications to the A500 mobo to make it see the trapdoor-memory (which otherwise is used as "slow"RAM). Those modifications can be as simple as opening one (soldered) jumper and turning the RAM-expansion of, but that depends on the revision of your A500 mobo.
