How do i disable IMAP and POP3 on tenant level?

[Deleted]

I was just wondering is there any way to disable them globally rather than disabling for all mailboxes?

[#2]

Nope, but you can add this as part of your mailbox provisioning scripts.

[#3]

To add to Vasil's comment, here is the article that discusses this. As you can see at the bottom, they recommend PowerShell. https://support.microsoft.com/en-us/kb/2416434