Multiple queries

I am a distributor and retailer of electronic products. I was registered under State VAT but I am not registered under Service tax and Excise. Now I got myself provisionally registered under GST. I use to purchase from within the state and outside the state. I have following queries:-

1. As from 01/07/2017 GST is applicable, there would be input of VAT on the stock as on 30/06/2017 which has not been claimed, how can that input be claimed??

2. Is there any provision to get registered under excise to claim the input??

3. The input of excise on stock can be claimed by manufacturer or distributor??