can i use my rtr cars controller at a race/pratice? <i like him

You can, but you wont have as much runtime because there arent as many frequencies on the AM band.

yes
as long as your freq. clip is there for you to use. Wouldnt want 2 cars running on the same channel

And Traxxas Junkee, that wouldn't necessarily be true, with all those going spektrum now, the regular "clip" channels have opened up quite a bit.

Not last time I was there for practice, I'm sure the AM are open alot more during racing, but everyone just getting into it that still has the stock radios are going to be there. last time when travis was there he ran like 2 tanks total on 2 AM channels.