Hi,
Just To Clear My Doubts Here about "multiple activation keys"
1. Can be use 2-5 machine at the same time ?
No, for that you require 3 or more pc license. Multiple activation here means, you can change mobo and cpu or some other part like hdd and the license will still activate properly till around 5 times I think. This is valid only for Retail and volume license keys. Single activation key like OEM key will not work the second time if its not saved in bios or key has not been deactivated before reinstalling the OS a second time.
2. If above point is YES....Say if I activate in 3 machine at the same time then I have 7 time left Out of 10 Activation...Right ?
Only if you have a key which has not been used by anyone else. IF you bought it online then it might have been sold to more than 5 people even before you bought it.
3. If one of Above 3 mentioned Mobo+CPU gone - I can activate with new Mobo+CPU but now I have 6 out of 10 Activation Left ?
yes.
OR
4. If a user activate for 5 machine after purchasing Key - He can reactivate one more time right ? Activation locked with same Mobo+CPU ?
yes
OR
5. With MSDN key you can't change the MOBO+CPU?
You can change both mobo and cpu.
With MSDN subscription you get only 1 key for 32/64 bit OS of WIndows 10.
MSDN key is meant for testing purpose only. Its given to companies for testing their software products before releasing to market. Its not meant for home use.
With this key you can install on 10 different pc simultaneously and all will activate. You can't use it on more than 10 pc at any time. If your pc hdd fails or cpu fails or something happens you will have to get new key if you have already activated the key 10 times. If not you can still use the key to activate again.