A Unity ID allows you to buy and/or subscribe to Unity products and services, shop in the Asset Store and participate in the Unity community.
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It is possible, UE4 has it. I don't see why unity can not do it. The main take here is, performance and point mentioned by superpig.
Very long time because they have to review every single application. If they do not contact you within 6 months, then it is weird and something to...