Converting units/buildings

I've got some questions about converting units/buildings:

What charactaristics are actually converted, which not?

1) If you convert an archer and then upgrade to x-bow, that archer will be upgrade too, won't it?

2) If you convert an archer but already have the x-bow upgrade, will it be an archer or a x-bow? And if it is an archer, will it upgrade to arb when the tech is researched?

3) I heard that if you convert a hun stable, you'll get the 20% bonus. What happens if you convert british archers? Do you still have the +3 range? (or will he forget that once he is converted 11) So you could have elite longbowmen with thumbring?

Have you done any experiences on the stuff above? Thanks in advance for helping me understanding the conversion system. :)