Yes, currently selling on 6 accounts, about to add 4 more.
If you use a tablet, phone, they can definitely identify you, even if you clear it out and start over.
VPN's, Proxies, MIFI's will work just fine.
For MIFI, I suggest you make sure you change the IP before switching accounts.
So the same rules apply to Mercari, you need to make sure you have a bank account that doesn't care about mismatch name deposits.
When I give Mercari a name, I just use the madeup name for that account but I use banks that don't care about mismatch name deposits.
I think the above answer should work for this questions.
For the most part MIFI's are not
Static IP's, but if you go with a MIFI, you need one that can give you a new IP.
Yes, unfortunately you do need to use the App to respond to offers.
I use a combination of MIFI, Proxy.
I use Proxies + an android app called "Postern".
You would need 1 for each stealth.
So let me explain what I'm doing now.
I am currently using an Android Emulator on my PC, each Emulator is running Postern with my Proxy. There's a few other issues that I deal with but I don't have a lot of time right now to explain.
Here's how it looks on my PC, these are 3 Emulators running, each with a Proxy.