What range of Bluetooth UUIDs can be used for vendor defined profiles?

Question

I want to build a simple Bluetooth Low Energy-based application using a custom profile. The adopted profiles / services / characteristics / descriptors use 16-bit U

Answer 1

All of the 16-bit and 32-bit UUIDs above the base UUID that you show above are reserved for items in the spec (or future specs). So vendor apps are free to use any 128-bit UUID less than the base UUID. There is no reserved space for vendors to use 16-bit or 32-bit UUIDs.