Tv Tuner Question

I’m new in the world of tv tuners so i need some help.

Right now I have Cable TV, The cable box goes into my VCR then into the TV. With an external TV tuner card can i connect it to my VCR? Does the TV have to be on or on the right channel to record? Can the tv tuner record on many channels at the same time. Can i put my tv tuner on a sort of “silent” mode to record, so that when i’m watching tv it will not affect the recordings?

You may be asking which tv tuner? Well i need you to suggest to me one that is external, can record many channels at the same time (Not a nessary), doesn’t need to tv to be on or on the right channel, when i watch TV it will not affect the records. ALSO, i’m in AUstrralia and i have Optus Cable, will it support?

thanks!