Guild Wars 2

I couldn’t find any further explanation on the internet how the “Reclaim the name” part of the name change contract works, i want to change my mains name into a name one of my alts currently has. Is i possible to change the name of my Alt and “Reclaim” that name on my Main character without buying 2 name change contracts?

No.
One name change contract gives you the ability to change the name once on one character.

Can you only change your character’s name once ever? Or could I theoretically buy 1 every month?

I don’t think there is any limitation on how many times you can buy and use a name change contract.

If you want to buy 10 contracts to rename yourself every day who is arenanet to stop you.