Can I use CURL for REST API requests?

Yes REST API requests can be sent via CURL. Please refer a sample CURL request to create custom collection below:

curl -X POST -H "Content-Type: application/json" -H "Accept: application/json" -H 
"Cache-Control: no-cache" -d 
'{ "apikey" : "E9047FDBA2F55DCC32A93475DA1FAB6D", "colname":"Custom_Collection", 
"coltype":"custom", "language":"en" }' 
https://localhost:8443/rest/v1/api/coladd

For more details on all possible CURL request read: CURL for API in SearchBlox