Afaict, you have to discard the snapshot 3 to return to snapshot 2. See section 3.4.4 of the User manual, downloadable in PDF.
To revert to an earlier snapshot, you right-click on the “Current state” item and
select “Revert to current snapshot”. This will bring the VM back to the state of the
nearest (most recent) snapshot. Similarly, you can merge several earlier snapshots
into one by right-clicking on a snapshot and selecting “Discard snapshot”.
Note: The snapshot reverted to will affect the virtual hard drives that are
connected to your VM, as the entire state of the virtual hard drive will be
reverted as well. This means also that all files that have been created since
the snapshot and all other file changes will be lost. In order to prevent such
data loss while still making use of the snapshot feature, it is possible to add a
second hard drive in “write-through” mode using the VBoxManage interface
and use it to store your data. As write-through hard drives are not included
in snapshots, they remain unaltered when a machine is reverted. See chapter
5.3, Configuring image write operations, page 78 for details