Is there a way to unlink the previous BTC address? I have a new BTC address and I linked it, now I have 2 BTC addresses, can I remove the old one which has zero balance?
No, why would you want to un-link? It doesn't serve any purpose and would be only a burden on Tonych to implement unlinking code. Just keep it linked, it doesn't hurt if it has 0 BTC. The distribution will be over in 3-4 months and it won't matter anyway.