it's definitely "shye shye" in Mandarin. in Cantonese it's more like "s", and many people mimic it trying to be funny or lighten up the atmosphere but usually they don't really speak Cantonese and can say it wrong and they also know it. other than this case, i think it's just because of accents, which i never heard before.

usually we use 海底捞针. it means "find a needle in a haystack" = nearly impossible.

you don't have to pronounce the whole 3rd tone in sentences like this, you omit part of it. just for the convenience of showing you how to pronounce it, i use 1234 to indicate the four tones, and *1 and *2 to indicate the former part (before the tone) and the latter part (after the tone) of the 3rd tone. so it's like this: wo*1 hen*2 xiang*1 da*1 lan2 qiu2. you may think wo*1 = wo4 and hen*2 = hen2. but they are different. you can compare them by just pronouncing *1 and *2 as they are in 3rd tone and you'll see the difference. i don't use any rules for saying them. maybe because Chinese is my native language and i've heard and speak a lot. it just sounds natural to me. if you didn't have the chance to listen and speak so often for now, just pronounce them as a whole 3rd tone. you may sound a little unnatural but people will always understand you and to be honest, many foreigners living in China for many years still can't get the tones right but they have no problem working and having conversations with locals. you can watch Chinese films and series to immerse yourself in Chinese environment. if not, you can always hone your speaking skill in the future when you have the opportunity to do so.

倒挺 is not a word itself. 挺 is an adverb meaning "very, quite", like 挺不错 = quite good, 挺符合 quite fits/maches. 倒 itself means "reverse, backwards", but here it means: 1. the thing you are describing is kind of beyond your original exception, but not too much, which means it's still logical and makes sense for you. 2. there are several characters of a thing that you are describing. its many characters are similar (all small, short, long, good, bad, nice looking, etc.) but several others are just the opposite. 3. you use it to express approval. sometimes all the above 3 meanings are included in a sentence. for example, a man's girl friend are so unreasonable and he dislike her more everyday. but she has a very obvious virtue: being kind and caring to old people, especially to her and her boyfriend's parents. so his friend can say: 她这人很不讲理，但对老人倒挺好。= she's very unreasonable, but she's quite kind to old people (our parents).

以前从来没听过，但我刚搜了一下，发现确实在华东（中国东部）部分地区有这种说法。在那边产好茶叶，人们有时不小心把茶叶喝到嘴里不会吐出来，而是咀嚼后吞下去，就有了“吃茶”的说法。具体请看这里（百度百科《吃茶》）：http://baike.baidu.com/view/755169.htm

not a problem. on 新华字典 there are only 250 most frequently used characters. if you spend some time to learn them, you will feel much easier even when you meet other characters cuz you can guess the pronunciation by looking at the components (they often have the same or similar sound). for example, 妈 means "mother", its pinyin is ma1. on the left is 女 meaning "female". on the right is 马 (pinyin ma3) meaning "horse", but 马 is used to give you some clue for pronouncing 妈. it's just an example, 妈 itself is a very common character.