I'm not sure which features from the third party apps are enable in the premium phones, like you mentioned. Care to elaborate more on that? However, you can't get Whatsapp fingerprint lock if there is no fingerprint sensor in that particular budget p...

You can't. However, you can always buy one though if you can afford.

You can use Office 365 applications for free in mobile phones, but it's not free for tablet, laptop and desktop computers.

Else, you can subscribe to Office 365 either Home or Personal license, which will cost you around US $70 for Personal and $100 for Home annually. There is also monthly subscription.

You can try Office for web, which is a free Office online applications. You just need a Microsoft account, a browser and active Internet connection to use the Online applications (Word, Excel, PowerPoint).