Case of past indefinite tense. 'Can' and 'can be' are used for present tense, and 'could' is used for past tense. 'Could be' is used for past continuous tense and for passive voice.

This is a case of probability of an action/event. In cases of probability, we use either 'may be' (in stronger cases) or 'might be' (in weaker cases).

Case of present perfect tense. 'Will have' and 'shall have' are used for future tense. 'Should have' is used for a piece of advice. In cases of certainity like this, we use 'must have'.

This is a case of advice (which needs to be accepted). Modal 'must' is the best usage here. 'Could' and 'had to' refer to past tense. 'Would have' takes the 'third form of the verb'.

'Should' is the correct option because when an opinion is given, it is very much stressed upon. 'may' and 'might' are incorrect because they are used when there is any type of uncertainity. 'should have' is unsuitable because in the sentence first form of the verb (do) is used.

When we ask for 'wish or desire' of someone, we use modal 'would'. For example: 'Would you like to have some snacks with tea?'

If the principal clause of a sentence is in past indefinite tense, the subsidiary clause takes modal 'would'.

This is an optative sentence, where a wish has been made. In such cases, we always use modal 'may'.

Case of past indefinite tense. We use modal 'used to' to refer to a habit of the past.

Usage of 'to' in the sentence qualifies none other modal than 'ought'.

Case of past indefinite tense. To mention about a habit of the past, we use modal 'used to'.

The sentence implies that nobody has the courage to go against his wish. Modal 'dares' best expresses the same.

Case of future tense. We generally use 'shall' for the first person.

Case of future indefinte tense. 'Shall' is generally used for the first person; modal 'need' takes 'to' with it; 'used to' is used for past tense. Modal 'will' is the right choice here as it is used for the second and the third person in the case of future tense.

Case of future tense, where some determination is implicit in the sentence. Though generally we use modal 'shall' with the first person(s), but in such cases we use modal 'will' (to show the determination).

Case of certainity of probability. Whenever we want to show the surity of an event, we use modal 'must'. Hence, option 2 is correct.

This is a case of request. Modal 'may' is used for requests, but in case of more humble and polite requests (as shown here by the usage of 'please') we prefer modal 'could'. 'Can' is generally used for seeking permission in informal cases.

Case of ability. Modal 'could' is the correct answer.

This is an optative sentence, where a wish (not a prayer) has been made. We prefer 'would' in such cases.

Case of advise about a responsibility. Modal 'should' is used in  such cases.

Case of past tense. Whenever we use the term 'wish' in cases like this, we use modal 'could'. It implies that 'if I had the ability to do that, then I would have done'.

'If I were you' here reflects a wish. In case of wishes subjunctives 'were' and 'would' are applicable if the present tense is involved. 'Had' and 'would have' will be used if past tense is involved. Example: If i had been there yesterday, i would have......

This sentence mentiopns the 'ability' of a person (present tense). Modal 'can' is the best usage in such cases.

Case of advice. We use modal 'should' to offer some advice.

Case of an obligation. In cases where someone is bound to something, we use modal 'have to' or 'must'.