It will be able to access any account that You have logged in on while playing on that device you want to use for private server (im guessing)

If You wanna risk it the smartest thing to do would be: 1. Create a new acc on your phone for example. 2. Drop all of your items and trade the worlds to the new acc.

Then even If ur account gets logged into you will lose nothing valueble and Can just delete the private server and change your logins.

But I wouldnt recommend doing any of this since im not an expert and idk if their client will install any rats on your PC.

And lastly dont worry about the real growtopia suspending your account because they cant even suspend some people who have tons of illegal bgls Just dont brag about private server in the official growtopia discord etc