T-Mobile USA has confirmed with BGR that the Sidekick 4G will be available to customers on April 20th for $99.99 with a new two-year contract and after a $50 mail-in rebate. The Sidekick 4G — built by Samsung — runs Android 2.2 (Froyo) with a custom user interface that should appeal to Sidekick fans. It offers a throwback QWERTY keyboard with rounded keys and is powered 1GHz Cortex A8 Samsung Hummingbird processor — that’s more power than any Sidekick before it. As its name implies, it will also run on T-Mobile’s 4G HSPA+ network. We really enjoyed using the Sidekick 4G during our hands-on at CTIA 2011 early last month, and we think Sidekick fans should be excited to get their paws the device that promises to revive the brand.