If it were possible to use the same USB stick with another operating system, for example to store files to use on Windows, a virus in the other operating system could corrupt your Tails.
To store files in your TailsUSB stick, use the [[Persistent Storage|doc/persistent_storage]]. To exchange files between Tails and another operating system, use a separate USB stick.
No. Upgrading whenever you get a notification from *[[Tails Upgrader|doc/upgrade]]* is enough.
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No.Tails provides upgrades every six4 weeks, thatwhich are thoroughly tested to make sure that no security feature or configuration gets broken. Updating add-ons in <span class="application">Tor Browser</span> might break the security built in Tails.
Our team sometimes publishes emergency releases, whenever important security upgrades are available in Debian or *Tor Browser* before the next scheduled release.