What Can I Wear? - Clothes Words and Terms

English has several ways of spelling the '-er-' sound, but 'Shirt' is the right one here.

Beware! English refers to several everyday pieces of clothing, using plural words (often 'a pair of ... trousers / shorts' etc.). This is because they have two halves that are mirror-images of each other, like a pair of glasses.
In plenty of other languages ~ maybe yours ~ the names for these things are singular, for the very logical reason that they are only one piece of clothing (not like a 'pair of shoes / gloves', which really are two separate pieces).
So, be careful with these in English!

'Pyjamas' (with a Y as the second letter, unless you are American) are plural in English. because they have more than one part: a top and a bottom. We call them 'a pair' again, because they usually match (i.e. with similar fabric and colour), even though the top and bottom pieces are slightly different shapes to allow for the human body!

The strap that we put round our 'middle' is a belt. 'Suspenders' (in British English, at least) are what some women wear to keep the top of their stockings from slipping down. Americans use this same term to mean what British speakers call 'braces' ~ which are straps that come off the top of the trouser, go up over your shoulder and back down to the trouser top.

'A undershirt' won't work in English (it would need to be AN undershirt, which isn't what the question said); in any case, that is another American usage. In Britain we call this a vest.
Yes, we know, the 'vest'-word for most of you means the thicker piece of clothing that we call a jacket: an 'outer garment'. But not in English! And it is usually worn under the shirt, on the inside, next to the skin.

In English we usually give the other details first (what colour, shape, fabric, etc), before we say the name of the piece of clothing.
The long, single garment that a woman wears for a formal event is usually a 'dress' (plural: 'dresses') in English, rather than a 'frock' ... 'frocks' are usually less formal, the type of thing you might wear for an afternoon or evening garden party with friends. A robe (in English) is usually only worn in a ceremony ~ by someone very important like a king, queen or bishop, or the chancellor of a university.

When we are applying several adjectives to describe something, the order is usually:
1. Any other description that doesn't come in the rest of the order below (e.g. an opinion: 'dear', 'nice', 'nasty', 'horrible' etc.)
2. Age (usually, 'old' / 'new' )
3. Colour
4. Origin (where it comes from, e.g. 'Chinese')
5. Material (what it's made of, e.g. 'wool' / 'cotton')
6. Purpose (what it's for, e.g. 'driving gloves', 'riding jacket', 'safety hat')
7. ... and then, at last! the name of the thing itself.
Coming from many other languages, this may seem very strange: you may instinctively think it makes better sense to name the thing first and then give the other details later. But that's not how we do it in English!
Beware also, that if you are explaining the origin of something (like these Spanish boots), the nationality always starts with a capital letter. This detail, too, is different in many other languages. At least English does you the honour of naming your nationality with a capital letter! ('A Japanese screen', 'A Peruvian poncho', 'An African ornament' etc.)

None of the others is right here. Answers 1 & 2 are 'generic', i.e. they do mean headgear, but they do not make clear that it has to be physically hard. A hat or cap is probably made of soft wool or felt (or even plastic) but it would not protect your head very effectively against a sudden impact.
'Casket' may sound or look quite like 'casquette' (in French), but in fact it is American English for a coffin ( = the box in which dead people are buried).
We should probably move on from this rather sad and serious topic!

Answer 3 is the right one (even if you are not going to eat dinner; you might be going to an important play, concert or meeting). You would also wear a white shirt (sometimes known as 'a dress shirt' ~ which may seem confusing, but it means the kind of shirt you put on when you are dressing for such a formal occasion), and a bow-tie.
Women, meanwhile, would probably wear a long dress or 'gown', and maybe a few pieces of 'dress jewellery' (necklace, brooch, tiara etc. if it were a really smart occasion!)

See the note to Question 7 for help with untangling this one!