A Blynk local server can be accessed from anywhere if you forward the correct ports and use a DDNS service if you don’t have a static IP address.
The only time you wouldn’t be able to do this is if your ISP uses a double NAT system.
Read this for more info:
No, not for what you want.
That’s slightly different to what I was discussing for the ESP-Now functionality, but either approach will test your coding skills (and aren’t really necessary unless you’re planning on using ESP-Now).
Pete.