Past Subjunctive - dürfte + past participle + haben vs. hätte + infinitive + dürfen

Question

A few questions about different subjunctive sentence constructions:

1. Sebastian Kurz dürfte sich für die zweite Option entschieden haben.

I read 1 to translate as 2:

2. Sebastian Kurz should have opted for the second option (the second option was in fact chosen, and Sebastian Kurz ought to have chosen it).

Question 1: Am I correct to think that 3 would be translated as 4, and that there is a slight difference in meaning between 1/2 and 3/4?

3. Sebastian Kurz hätte sich für die zweite Option entscheiden dürfen.

4. Sebastian Kurz should have opted for the second option (but he did not in fact opt for the second option).

So it seems to me that the different grammatical construction of 1 (subjunctive modal verb + past participle + haben) and 3 (hätte/modal of 'haben' + infinitive + modal verb) captures a difference in meaning. Question 2: Applying this to the verb 'können', am I correct in the translation of 5 to 6, and 7 to 8?:

5. Ich hätte den Apfel essen können.
6. I could have eaten the apple (but I did not in fact eat the apple, and we do not know whether the apple was in fact eaten)

And:

7. Ich könnte den Apfel gegessen haben.
8. I could have eaten the apple (the apple was in fact eaten, and I may have been the individual who ate the apple - though someone else may have).

But what then is the right translation for 9, where we drop the subjunctive form of the modal verb, and use the simple past for the modal verb instead? Question 3: Would it be the following?:

9. Ich konnte den Apfel gegessen haben.

10. I could have eaten the apple (the apple was in fact eaten, and I had the ability to eat the apple - though we do not know whether I did in fact eat the apple or not - someone else may have)

Answer 1

Note that dürfen in past Konjunktiv has a special meaning, roughly translating to "is supposed to". Your translation of (1) is thus

Sebastian Kurz is supposed to have decided for the second option.

The translation of (3) is also somewhat off. It rather is

Sebastian Kurz would have been allowed to decide for the second option

Your translation of (5) and (6) is, in fact, correct, the rule is pretty simple - The verb that carries the Konjunktiv is the action that is not real (in irrealis).

(9) is a bit odd - sounds a bit like a murder investigation on an apple, but grammatically correct, your interpretation as well.