I am currently at my "opened" Anytone AT-779UV in the house, programmed for GMRS (but with more options), with Firmware 2.26 (my Radioddity DB20-G programmed for "locked" GMRS with firmware 2.30 is in the car right now), so my comments are based upon my playing with this Anytone.
1) Holding down the FUN key for a few seconds will LOCK the keypad/mic buttons (one beep). Let me know when you figure out how to UNLOCK it!?! hahaha. Of course, holding down the FUN key again for a few seconds toggles this feature (two beeps).
You can also toggle this same "locking" feature by holding down the A button on the mic/keypad.
2) I believe you are referring to Menu 19: DSPSUB, which has these 3 choices of settings. You can get to this without the software by pushing the FUN button once and then scrolling through the Menu with the V/M (Up) and MAIN (Down) buttons. You then change the settings using the Up (Arrow) and Down (Arrow) buttons and when you are happy with your settings, push FUN again to exit this mode.
3) I am not sure what you are asking here, because I probably don't have any experience here. But I want to learn, so please educate me. Is this in the software?
4) By "Busy Channel Lockout" I believe you mean a setting which will prevent the radio from transmitting while it detects someone else using the same frequency. I am looking into this for you.
UPDATE: Look at the manual's description of Menu Item !!: RPLOCK, below and see if this does what you want; again using the FUN button will get you into Menu Mode: