Had it on summer

Had it on summer
 

p.251
-I had it on holiday summer before last.

1. Does this mean we could say on summer?

2. If on is not with summer, is the before summer just optional?

For a definitive answer, more context is needed, but on holiday sounds better. There may be some cases when with can be used, but less commonly. This is British English, by the way.

"...(while) on holiday ((during) the) summer before last" is 2 distinct phrases:
a. "on holiday" (or "while on holiday") (British English, = US English "(while) on vacation"
b. "summer before last" (or "the summer before last" or "during the summer before last")

"I had it on summer" sounds wrong to me.

Excellent answers. Thank you.