There's really not much we can tell you in this situation if things are strictly controlled by your parents. Even if you get your network sorted out, NSO subscription is something you MUST pay.
Though I can suggest you some ways here:
For the network:
1. If you got your PC in a room and it is connected to the internet via LAN cable, you can get a USB to LAN adapter (it's embedded in a dock if you have the OLED one), and plug it in. only works if you're using a monitor to play it.
2. You can extract the wifi password from your android or PC. I don't remember the details so you gotta search that up
3. In most of the recent phones you can start a Wifi hotspot from your phone, while being connected to your home wifi. The connection quality would be bad but if your parents are monitoring a network to see if you're not using any additional devices, this could work (though that'd be very extreme case)
For paying the NSO:
1. In most countries they do sell prepaid NSO codes offline which you can purchase with physical money, and I believe they cost like $25 for a year. It's a fair deal imo, especially if you're planning to constantly play throughout a year.
2. In some countries you can also get prepaid VISA which I believe you could use for online payments. You could then purchase your subscription from E-Shop, though I think this is less likely the case compared to 1
3. If it's too much, often times there are people who will share the family subscription where one only pays for 1/n of the price. It is way cheaper compared to buying it for you alone, so if you have access to something like paypal or any ways of sending money between individuals you could look into that.