Hi,
Not sure if this helps you but here goes:
1) No. As far as I know you cannot remove the app and install a new one. The BT is part of the firmware IIRC. Try and find your NavAll version and start looking for firmware. You will need it (now or in the near future)!
2) That depends on which NavAll you have. Can you provide or find which NavAll you have?
3) There are tons of threads concerning SWC and the color of the wires. It is usually a separate cable with a yellow connector and an orange/blue and orange/green wire. Search this forum section and I am sure you will find a zilion posts with photo's
4) Any misbehavior of the NavAll is comon I am afraid. I think you will have to be forgiving with it
As a bonus tip I can advise you to use the search function because all versions of the NavAll have been discussed at length. Most problems you encounter others have already dealt with. You just have to look for it
HTH