Yes, and a good example of a place where you need to use the verb form "had had." "Learnt" is OK, but slightly old-fashioned. It's an example of several words that can be formed either with -t or with -ed. Another example is "sunburnt" = "sunburned."

Yes, this sentence is correct as I can see. However, "learnt" is not as commonly used in the States. Typically the past tense of learn is "learned". But both are correct, I believe. Also, learned sounds better in this context as it's describing English and what could have been done.