ct code

On my PRO-164, if I program a CT code and it is incorrect, will it prevent me from hearing anything on that channel?

Hello. I'm pretty new to the scanning world. I'm using a PRO-164 and I come seeking knowledge! How do I know if I should use CTCSS or DCS for a frequency? It seems that for most of the Police or Fire frequencies if I use CTCSS, a code will show up on the display and when two parties are...