If my opponent plays Singularity, can you react with 2 reaction spells?

Yes, you can react with two reaction spells in response to your opponent playing Singularity.

According to the rules regarding the chain and reaction spells:

• Singularity starts a chain: When your opponent plays Singularity, it is placed on the chain.
• Reaction timing: According to Rule 155.2.b.3, a spell with the Reaction keyword resolves before spells and abilities already on the chain.
• Multiple reactions: You can play a reaction spell in response to Singularity. Once that reaction spell is on the chain, your opponent (or you, depending on priority) has the opportunity to respond to that reaction spell. You can continue to add reaction spells to the chain as long as players have the opportunity to respond.

As noted in the FAQ regarding Singularity:

"Singularity does not trigger a showdown, but it does start a chain. Opponents cannot respond with action cards like Primal Strength, only reaction cards can be played in response."

Because reaction spells are played during a closed state (the chain is open), you can chain multiple reaction spells together before the chain resolves. Each reaction spell you play will be added to the top of the chain and will resolve before the spells beneath it.