The code buttons are for testing only and will not change anything on the machine. I repeat they will not change anything on the machine. The only area that the customer can make adjustments is in the menu area. It is not a good idea to play with the buttons except for making adjustments to your settings. You may jeopardize your warranty.
I was able to change my dredgedraw alert to twenty portions ( from 30) to make sure I don't miss cleaning it ( also at 30, the machine got messy)
I know better then mucking with things I don't have inside info on, but there are some good settings I'll certainly be tweeking with a very little bit.
My machine was listed as being made on valentines day of 2000.
For high altitude use, looks like you can adjust the thermal cut outs.