veya and ya da are really synonyms and they are not like the examples you gave. Your examples are regional variations as you mentioned. Sometimes some vowels are dropped as in the examples of içeride - içerde, dışarıda - dışarda, nerede - nerde, burada - burda. Bacı is a word that I never used and I will probably not use in the future. In some regions it just means a sister or a sister-of-law but in modern contexts it's old fashioned. and it's usually considered to be rude to address someone you don't know using the word bacı. It's still a cultural thing though.