I'm not sure I understand your question entirely. You should be able to fill all fields in a form. If you are not able to do this, can you please share more information about what you are doing and send the form to firstname.lastname@example.org?
Thanks for sending me your form. It's a fantastic form for use on a tablet so we were very excited to see it! We have identified the problem and are working on a fix for a future release (timeline still unknown). Here is the issue described for others who may be experiencing the problem:
If two fields share a common name, those fields should be updated in tandem. That is, if field A and B are named "FirstName", field B should be updated with the value from field A when the user fills in field A. Similarly, if the user fills in field B, the value in field A should update.
Unfortunately, there are two pieces of the field that require updating and our Reader currently only updates one of them which means this functionality isn't working entirely. When the user updates field B, field A does not seem to be updated. Similarly, when the user updates field A, field B does not seem to be updated. We have filed a bug and hope to address it in an upcoming release. You may have noticed that it is ALMOST working. If you were to tap in field B after editing field A, I think you'll see that the value is present in the activated form field. We need to fix this so that the value updates without having to activate (tap on) the second field.
Thanks again for reporting the issue!