Even after enabling Shield platform encryption for a field, say, Account Name, the Name of an account is shown in plain text.
View Encrypted Data permission has not been given to the user.
According to https://releasenotes.docs.salesforce.com/en-us/spring17/release-notes/rn_security_pe_masking.htm encrypted fields will no longer be msked.
So is there any way, if the field value is getting encrypted or not?

In the connected App OAuth policies, I have selected "Refresh token is valid until revoked" in Refresh Token Policy.
But some times the refresh token gets expired and I get { [invalid_grant: expired access/refresh token] name: 'invalid_grant' } error. After getting a new refresh token, it works fine.
Ideally the refresh token should be valid for lifetime or until revoked.
Can someone help me with the reason behind this. 

Platform Encryption can be enabled for an organization through Salesforce UI by selecting 'Enable Encrypted Standard Fields' under Set Up -> Security Controls -> Platform Encryption.

Can the same thing be done through API Access?

The OAuth Scopes assigned to a connected App in Salesforce can be retrieved from the Salesforce UI in the App details.
Is there any way to retrieve these data through REST API? 

The Admin in an Organization by default receives the Chatter Feed updates for any post created by other users. All posts in an Orgamization can be listed in the list of All Company feeds. Is there any setting to disable these Chatter Feeds, so that the admin won't recieve any updates?

Through Chatter REST API, it is possible to get list of files per user using following query:
/services/data/v34.0/chatter/users/00590000003A2nmAAC/files
In order list all files in an organization, we need to query for all users separately which will result in consumption of so many API calls.
Is there any way to get all files in an organization using a single API call?

We can get the list of items in the Force.com app menu or App Launcher from the 'AppMenuItem' sobject. This cotains a field 'ApplicationId'. If this is the Id of the application for the item in Force.com, there might be an sobject which contains a row with id as this value. My purpose is to get the list of apps installed from appexchange or created in a salesforce organization. The records in 'AppMenuItem' sobject doesn't contain any field indicating the category of app, for example, Standard or Custom or Console. The value of 'Type' field indicates if the app is a connected or ServiceProvider or TabSet app. 
There is another sobject 'PackageLicense' represents licenses for installed managed packages. This sobject also doesn't have enough details.
Any help is highly appreciated.

The apps in Salesforce can be Standard or Console or Custom or Connected apps. The apps downloaded and installed from Salesforce appexchange will fall under which category?

Platform Encryption can be enabled for an organization through Salesforce UI by selecting 'Enable Encrypted Standard Fields' under Set Up -> Security Controls -> Platform Encryption.

Can the same thing be done through API Access?

The OAuth Scopes assigned to a connected App in Salesforce can be retrieved from the Salesforce UI in the App details.
Is there any way to retrieve these data through REST API? 

The Admin in an Organization by default receives the Chatter Feed updates for any post created by other users. All posts in an Orgamization can be listed in the list of All Company feeds. Is there any setting to disable these Chatter Feeds, so that the admin won't recieve any updates?

Through Chatter REST API, it is possible to get list of files per user using following query:
/services/data/v34.0/chatter/users/00590000003A2nmAAC/files
In order list all files in an organization, we need to query for all users separately which will result in consumption of so many API calls.
Is there any way to get all files in an organization using a single API call?

We can get the list of items in the Force.com app menu or App Launcher from the 'AppMenuItem' sobject. This cotains a field 'ApplicationId'. If this is the Id of the application for the item in Force.com, there might be an sobject which contains a row with id as this value. My purpose is to get the list of apps installed from appexchange or created in a salesforce organization. The records in 'AppMenuItem' sobject doesn't contain any field indicating the category of app, for example, Standard or Custom or Console. The value of 'Type' field indicates if the app is a connected or ServiceProvider or TabSet app. 
There is another sobject 'PackageLicense' represents licenses for installed managed packages. This sobject also doesn't have enough details.
Any help is highly appreciated.