Forming Past Real Conditional sentences

Question

I began recently to study English conditional sentences and now I'm trying to find information about Past Real Conditionals formation (as I understood, they are also called Zero Conditionals in other classification). There is not much info on the Web on this theme so I write here.

As I understand now, in either of the clauses - dependent(condition) clause and main(result) clause - we can use in any combinations:

1. verb in any past tense (i.e. Past Simple, Past Continuous, Past Perfect, Past Perfect Continuous)
2. constructions of type: modal auxillary verb + infinitive of main verb, with infinitive being able to express any aspect (i.e. we can use bare infinitive and various infinitival constructions like, for example, "be being written", expressing continuous aspect in passive voice, "have been writing", expressing perfect continuous aspect in active voice, etc.)

Please, let me know if it is right, and, in particular, provide me with some examples of sentences, which don't have the most obvious variant of structure in which both dependent and main clauses have verbs in Past Simple tense. The more nontrivial examples are, the better it will be.

Answer 1

Zero conditionals are formed with present tense in both the "if" clause and the main clause

If the temperature is above 100, the water boils.

It doesn't really express a "condition" just the direct linking of two events.

Past real conditionals describe events and consequences in the past

I was always very polite when I was at school. If I met my friends, I bowed to them.

It would be correct, and perhaps better to say "When I met my friends..." or even "Whenever..", and the result clause could be "I would bow to them" or "I used to bow to them" (indicating past habit). This is "real" conditional, describing events that actually occurred, and the consequences. In contrast, consider the counterfactual:

If I had met my friends, I would have bowed to them.

You can make a past real conditional more complex:

If Peter was playing guitar the neighbour would bang on the wall.

Here there is a past continuous in the if clause, and "would+infinitive" in the main clause. Again, it should, perhaps, be expressed with "whenever".

I used to be given chocolates at Christmas, if I'd been well-behaved the previous year.

(Used to with passive voice in main clause, past perfect in condition.)