Defense and dodge are handled with the same function (they're one and the same), as long as your Armor Class is superior, you'll dodge/parry the attack. That's up to you on how you want to roleplay it, although Bell's skills are specifically designed with dodge in mind (like the riposte or feint).
The magic potion exist for the early stages of Bell (When he starts with little MP), and eventually once he gets a lot of Mana, they'll be needed for chanting spells that consume hundreds of MP.
Liliruca's only spell is transformation which is used in the "novel" part, and welf's will-o-wisp hasn't been added yet (it'll be available in the next and final release).
For stronger potions, you need to finish the last quest of the Blue Pharmacy which unlocks elixir (and watered elixir) which heal 100% or 50% of HP accordingly.
Welf's portrait and other graphics are a result of years of changing, experimenting and improving. Hence why the game kind of changes look as you progress, on the last release some characters will get an overhaul, such as Lefiya:
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However, not all of them will. Old and outdated sprites will instead be redone for the sequel.
The last release of Legacy of Hestia will be on January, you can read about the current changelog here:
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