Forum Upgrade from 3.8.7 to 4.2

[محروم.كوم]

Sorry to start a new thread about this but i've searched and didn't get the answer i was looking for. The idea is that my forum currently runs on 3.8.7 but i decided to finally go for the upgrade. What bothers me is that the original version got a customized template which is definitely not compatible with 4.2. So i got a custom theme for the new forum as well. However before going live with the upgrade i want to do some tests so i can see how the new design will look like, that is why i want to know what's the easiest way to restore a copy of the 3.8.7 vb on a 4.2? Is there any way to do it? __DEFINE_LIKE_SHARE__