Is arbitrum available on Coinbase?

Yes, Arbitrum is currently available on Coinbase’s centralized exchange. For more detailed instructions, check out our helpful how to buy Arbitrum guide. Certain content has been prepared by third parties not affiliated with Coinbase Inc. or any of its affiliates and Coinbase is not responsible for such content.

Is there an arbitrum crypto token?

At the time of writing, there is not an Arbitrum crypto token. Ed Felton, co-founder of Offchain Labs, stated in 2019 that they don’t plan to launch a separate Arbitrum token. For those looking at how to invest in Arbitrum, there is no direct method, let alone any ARBI price predictions.

Is Coinbase the same as Coinbase wallet?

Annoyingly, Coinbase isn't the same as Coinbase wallet. I suppose I should have clarified with OP as to what he was using, but since he only said Coinbase I assumed he meant the CEX part, not the self-custodied wallet part. Coinbase wallet does support Arbitrum which is pretty nice, but you can't withdraw from there to Coinbase itself.

Is there a safety net if Coinbase doesn't accept Ethereum?

There are no safety nets. When making a bank transfer, they ask you to provide a name and then if it’s a match you get a confirmation. The payment should have bounced if Coinbase do not accept ethereum sent via the Arbitrum network. Yes we can all make mistakes and I am sure we all regret what we did.