#Can regular players open the admin console?

No. The console only opens for the place's own Roblox creator (your account or group) and anyone whose UserId you've added to Config.Admins.UserIds — every command re-checks admin status server-side on every use, so a modified client can't fake its way in, and the button that opens it is hidden client-side for non-admins too. See Admin Console — Basics.