Welcome to the forum, Zote.
One problem is that different dictionaries use different notations. Each time you use a dictionary, you need to check which system is being used. It is very difficult to answer your questions, because we don't know which sybols you re using.
A second problem is that a symbol between square brackets, , is a phonetic symbol. This symbol will be pronounced in exactly the same way by every phonetician in the world. A symbol between dashes, //, is a phonemic symbol, and will cover a range of pronunciations that will are considered the same sound by native speakers.
A third problem is that speakers of some varieties do actually use different sounds within the same word. For example, some speakers of AmE use the same vowel in the words 'cot' and 'caught'; most speakers of BrE a different vowel in each word.
If you want us to help, you need to ask about one sound or word at a time, and take your examples from one book or online source - and tell us which.