Will the 4.6 on Bold be compatable with 4.2 on previous devices, i.e. will the applications written for 4.2 function on 4.6? Appreciate the answer. Thank you.
For the most part, they will function. You'll need to put the program on the Bold and have a look for issues. For example, icons used on the 4.2 devices are extremely small on the Bold (due to the higher screen resolution).
Likewise, if you have any paint() code that assumes a particular screen size, you'll have issues.