There are two places where one "upgrades" a Mikrotik device: System -> RouterBOARD (your screenshot) ... which is similar to BIOS/EFI on a PC and is commonly referred to as routerboot in MT world ... and System -> Packages, which is similar to OS (e.g. Linux or Windows) and is commonly referred t oas RouterOS in MT world.
When upgrading ROS, there are a few channels: long-term , stable, testing ... and upgrade. After setting channel to desired one (upgrade is v6 channel, specific for upgrading to v7 ... and might not be available in your version of ROS, which is pretty ancient, newest is 6.49.18), you need to hid "update" which will contact MT's download server and check for newer versions within selected channel. Hitting upgrade will then upgrade to that newest version. Note that in v7, there is no long-term (yet) and obviously neither upgrade channel.
As to routerboot upgrades: ROS comes with matching routerboot images and after you successfully upgrade ROS (and reboot, which is standard part of ROS upgrade), you can go back to routerboard menu ... and you'll see newer version available.
And to the topic (VLANs): on CRS3xx there isn't a major difference in how VLANs are configured between v6 and v7, there are only minor differences. But I'd recommend you to upgrade to v7 never the less, notable difference for CRS3xx is wire-speed routing (with more ore less severe limitations depending on switch chip used in device), you can read about it in L3HW offloading.
And another (a bit lenghty but very good) document (a tutorial) about configuring VLANs on bridge: Using RouterOS to VLAN your network (it's a mystery to me why it became so hard to find it ... e.g. using google, IMHO it's worth reading it)
There's often confusion about what bridge actually is in ROS ... it has multiple "personalities" and this article tries to explain them: RouterOS bridge mysteries explained