Is this real gold or gold plated?

It is solid 14k or 18k gold, depending on the option chosen, and platinum is also offered. There is no plated base metal version.

Can I choose the chain length?

The listing gives no chain length or adjustable closure. Ask Capucinne before ordering if you need a specific length.

Can the medallion be set with a gemstone?

Yes. Capucinne says the design can be made with gemstones of your choosing, but you must contact them before purchase to arrange it.

Is it a good baptism gift?

It is designed for that: a cross and a Blessed Mother medallion in precious metal, gift-wrapped and shipped insured. Keep in mind the chain is fine and the pendants are small.

How should I care for it?

Store it separately to avoid scratches, keep it away from perfume and chlorine, and polish gently with a soft cloth. White gold and platinum may need professional re-polishing over time.