Here are some of the answers to your questions.
1. Permission for Android
Android operating system is designed to be secure for apps and users. So for every root level action requires an app for asking for permission during the install and during the usage. So every app that requires root level action asks you for the verification dialogue when the app is being installed. Considering the Android written on top of the Linux-based kernel, it's natural for it to ask for root permission for app usage. Disk partition, file copy, internet access, camera access are being kept under root permission. You can get over this limitation if you wish to format the disk by connecting the device to PC and then format it, using an external application. In such case, however, any data that you have, might be removed. In this case, you have to connect the Android device using ADB bridge, override the root and then get the access to the disk.
2. Mac Address Allocation
Every device that is connected to the network gets assigned with the IP address. And any device that routes the devices in a network is assigned with the MAC Address. So for example, Wifi router, Wifi hotspot, all are assigned with the MAC address. Unless your device itself is acting as a server for other devices connected, there is no need for it to have MAC address.
3. Different Address in Devices
Bluetooth, IMEI, IP all are handling a different level of communication and hence they are recognized as differently with the number. For example IMEI is the number that is assigned by the telecom operator so that is already unique for each device. Same goes for Bluetooth as it's different communication method and recognizes the device in a different way. And finally, IP is specific to the internet network, which assigns unique IP per session till the router is rebooted. The reason as explained is because each device has a unique connection established for different packet transfer within it's specific network.
4. Mobile Network assigning different IP
If you are connecting the device to Wifi with static IP, then your IP remains same. However as the mobile network doesn't have static IP system, you'd find it allocating different IP in a different session. You may find that device in a Wifi network with dynamic IP allocation also leads to different IP in each session.