Any members added to a Group Chat in Teams are not able to get the access to Previously shared files.
If they click on those Files, it comes up with the “You Don’t have access to this File- Request access".
I raised a ticket with Microsoft and the answer was that this is By-Design feature in Teams for the security purposes.
It gives the option to request for access to that file.
Files that are shared in a private or group chat are stored in the One Drive for Business folder and are only shared with the people in that conversation (People in the conversation at that time).
This creates troubles as the normal behavior is same as adding someone to a Team: if history is shared they will need to have access to previously shared files as well.

Feature request with regard to styling/branding and use of CSS: Please add a unique class and/or ID to EVERY main [div] in de HTML output of Office 365, but especially SharePoint. Currently I cannot address specific parts through CSS; for example I want to be able to change the look of a promoted links app on one page, but without effecting any other promoted links app as well.

Some CSS changes I made make the main [table] on settings pages drop below the navigation, currently I cannot correct this because the [table] has no ID or class. From website design perspective I find this a 'fail'.

I think if MS would implement this also in the modern UI, using custom CSS for branding and styling would become a lot easier for everyone.

You can use a group as a collaborative inbox to distribute and track responsibility for topics among the group's members.

These collaborative features are especially useful for technical support or customer service teams. For example, you can create a group with the address support@your-domain.com, add your support staff as members, and allow people outside your organization to send messages to the group. Your support staff will receive your customers' messages, and they can do any of the following from the group's Topics view:

Assign responsibility for a topic to a member of the group
Mark a topic as resolved
Edit the tags associated with a topic
Filter topics according to tag, resolution status, or assignee

we using the Skype manager to manage the skype credit for users to International call in Hong Kong, but we just started to skype for business and find the Skype for business International call is not available to Hong Kong. also i cannot find skype credit like function on our Office365 admin portal, i think that not yet ready on Hong Kong location. if that can make the call and manage skype credit easy as on the skype manager, then it can replaced the skype (free version).

also the Skype manager function is very good, the Office 365 admin should migration those function into Skype for business.

We were hoping that if O365 users added their birthday in their profiles, then it would automatically populate the birthday calendar, when it is turned on. To have to add that data manually, seems to be less productive. It would just be for the organization the user belongs to and would just be month and day. The profile allows users to enter year, but we don't have users do that. currently, you have to look at the user's profile, drill down through a menu or two to find the birthday date and then go back and add it manually. It would be nice to click on the data on their profile and add it, if they have set the permissions to be everyone. Currently, everyone can see it, but they have to go through a different process to add it.