I am new here, developing a billing system (for my own company) exclusively with Bitcoin payments. I am not a developer by profession, but I can understand code.I have started to test my billing system and I ran into a few issues:BIP32 library deriving addresses with very high indexes: 152340035. I though that was interesting until I couldn't find/make any wallet import those addressesMy developers telling me that the only functional testnet is testnet3 - but in turn finding that most of the Faucets for testnet3 are broken or deleted, and testnet4 looks more active/functional. Which is true? Is testnet4 functional?One of the wallets I am using (OneKey) seems to be able to receive coins for testnet4 faucets but another (Blockstream Green) seems not. I could transfer coins from OneKey to Blockstream. The wallets themselves don't obviously mention if they are using testnet3 or 4, they usually just have "Bitcoin testnet" as an option. Finally, are testnet addresses interchangeable between 3 / 4?Can anyone please help me with some Testnet Bitcoins - they seem to be harder to get than the real ones :)here is my wallet:tb1peu0qjlwx835q59r9akk3nngcryk8y9ke6apnk42mnzs0lgrxh6nq6cgm74Any amount will be appreciated.Thank you 🙏