You can no longer create a new PSN account directly from the Vita.
There are two main ways to get the 3.74 update on your handheld. 1. Official Over-the-Air (OTA) Update Ps Vita Firmware 3.74 Download BETTER
While the store remains open, certain payment methods have been restricted to improve security. How to Download and Install 3.74 You can no longer create a new PSN
Download the official PSP2UPDAT.PUP file from the PlayStation Support site . Place the file in your update folder and connect via USB. Firmware 3.74 and the Homebrew Scene Ps Vita Firmware 3.74 Download BETTER
Yes. Tools like Henkaku and VitaDeploy work on 3.74.