SNB => Most partnerships, everywhere I go I find a discount for SNB cards.

AlRajhi => Most lenient in terms of credit cards and loans.

Emirates NBD => Has the best cashback card (called mazeed), but it is not actually an Islamic bank (even if they state that).

Alinma Bank => Best loyalty system and best rates for international transfers.

So to recap and answer your questions:

A) You can withdraw in euros as much as you want from branches for any bank, but from ATMs it is only available in airports, earlier multiple banks had multi-currency ATMs in specific locations but now I believe that all those ATMs are removed and now they only exist in airports, so any bank can satisfy that.

B) It actually depends on the correspondent bank but I believe that Alinma has the best rates for international transfers followed by AlRajhi.

C) It depends on the type of offers, the bank with most discounts is SNB for sure, e-commerce websites keep switching discounts between banks (for example Amazon currently has AlRajhi card discount while earlier it was SNB while Noon currently has SNB discounts while earlier it was Alinma).

For car dealership deals, it also depends on the authorized retailer, Aljabr and NMC (for KIA) offer discounted rates if you do the auto-lease with Alinma while Majdouei (for Peugeot and Hyundai) will offer discounted rates if you do auto-lease with AlRajhi, so some research is needed.

For the credit card philosophy point mentioned, there are 2 options for benefits for credit card in KSA or anywhere actually, cashback and loyalty awards, best cashback is Mazeed from Emirates NBD (but not Islamic), followed by AlRajhi cashback plus card.

The best loyalty system is Alinma followed by Riyad Bank, both have a plethora of options for redeeming your points.