Which one is correct? "a specific situation" or "an specific situation"? I know "an" normally goes with words starting with a vowel but in this case...
Specific or specifical? Cynic or cynical? Clinic or clinical? Medic or medical? Juridic or juridical? etc. Specifical is not used. Cynic is a noun, while cynical is its adjectival form. Same thing with clinic and clinical, medic and medical. Juridical and juridic are both adjectives and have the same meaning, but the latter is rarely used.
as at is quite common in this context to mean at a specific time/date. "As of" to me means since. "As of" only rarely means "since" in AE, and it still sounds awkward and confusing to me, so I personally avoid this usage. Example: The washing machine was fixed as of last week. The meaning of this sentence is unclear.
There are other specific terms in many other contexts. If you give us more of the context in which you plan to use this sentence, or the subject of your essay, we might come up with some that fit. Lacking any context, the generic "things" is all we have. Added in edit: Cross-posted with the previous poster, who said the same thing in far fewer ...
Therefore, "Co." sometimes occurs with "Ltd." and sometimes it does not. In referring to a specific company, you should be guided in the use of these abbreviations by the organization itself—its stationery, literature, Web site, etc. Some companies insist on spelling out one or more of these terms in all cases, some do not.
I'm not surprised it's been driving you crazy! For a specific date, as in your first two examples, we use 'on'. For a less specific time reference, we use 'in'. You may think of it arising from 'The final is in [the month of] July', The final is in [the year] 2018. Therefore, the preposition for month + year, both of which are not specific dates, is 'in' – so you say 'The WC final is in July ...