What is the meaning of 'change' and 'reserve' in a Bitcoin Core wallet dump?
what is exactly the meaning of reserve and change? My guess is that reserve are normal reception addresses and change are, well, change, but I'm still wondering if there's some meaning more specific to Bitcoin Core.


reserve means that the key is in the keypool and has not been used yet. This is used for both change and receiving addresses as there are keypools for both.
change means that the key is used for change addresses.


I thought that change addresses were derived with a different path, like the reception addresses all end with ../0/{index} and change with ../1/{index}, or is Bitcoin Core doing things differently of say Electrum?


They are. Bitcoin Core uses m/0'/0'/i' for receiving addresses and m/0'/1'/i' for change. However if you have an older Bitcoin Core wallet, this split doesn't exist and there's only one keypool. But if you are using sethdseed, that shouldn't effect you.


Besides I wonder how to generate 2 different key pairs with the same master key and path, could I have generate the change address with libwally too?


There aren't 2 different key pairs with the same master key and path. Bitcoin Core doesn't do this, and that is not possible with BIP 32 (or any BIP).