Hi! So, I'm using GB Studio version 2.5.
For showing variables as text, you have a few a options. The first is display the current value of a variable, which can be done by placing the variable name/number between two $ signs in your dialogue box. For example, if you had a global variable tracking your XP, you could display $XP$ in any dialogue box and it would show it's value (0-255).
For the names, it's a little different. I have a variable tracking each letter. I then give the variable a value equal to the ASCII value of the character I want to display. In this game's case, it's just capital letters and spaces, but you can cover your entire ascii table if you needed. So if my character's name begins with "A", I have global variable "Name 1" = 65. Then, you can display it in dialogue by using the variable in between # signs. So to display a name, I write: #Name1##Name2##Name3# etc. I believe this has been available in most versions, but it's possible it's not an option in certain early builds of 1.0.
The advantage of ## over $$ method, besides showing ascii instead of just a number, is that the ## method always only counts as 1 character. $$ always counts as 3 characters because it needs to reserve space for an entire range.
The leveling system is just tracking an XP variable for each character. On the results screen, if you've reached a certain amount of XP (depending on your current level and your class), you can level up. The game runs a check and update your stats/unlocks new skills based on other variables that only trigger at those XP thresholds.