Guide says that anything created, even Permenants, need to be maintained.

- Create Wall, Door, Stone Block, Rose, Thorns, Boobytrap and anything else..

Do they need to be activated with magic and thus are actually temporary?

Can they be dispelled for free by the caster at any time?

Do they disappear once the caster has lost a life?

Can created walls & doors be dispelled?

Side question:

When a wall is destroyed with a card, is the damage directed away from the caster, or can they be injured as well (while adjacent)?

Permanent here means they do count towards the number of cards you may have (in hand + in play); this also means you can discard them at any time during your turn to terminate their effects (IIRC; it's two years since I played WW for the last time)

As for your side question: indeed, effects destroying a wall can damage also the wall's creator

the fact is the choiche you make before plays with your friends. Maintained spell have optional rules that make them counting on your hand size (most used when play with expert players) or not, so in the first everything you have played and not discarded/ended count, like permanent/temporary spells or items, the second permit permanent/temporary spells to not take space in your hand size.

wrote on rules, you can end any spell you cast in any moment of your turn before discard&draw phase

Rules for mantained spells counting against your hand size are not optional, they are core. Variants could consider this in a modified way, but not core rules

Rules for mantained spells counting against your hand size are not optional, they are core. Variants could consider this in a modified way, but not core rules

yes, true