It's a matter of style. UK English tends to use single quotes whereas US tends to use double quotes. There's no additional rule for individual characters. I don't think it's essential to use quotation marks when indicating an individual letter, but it may help for clarity. It helps when distinguishing between single-letter words and single letters, for example.
Saeed, is there a legal requirement for your site to use the right words? If so, you may want to check with a lawyer instead. If not, I think "individual" and "organization" covers them; the latter encompasses both for-profit companies and non-profit organizations. This is US-speak, at least.
Although the word individual sounds singular because it relates to one person, it is possible to have two or more individuals. This is the case in your sentence.
Individual animals take on specialized roles to ensure the entire group is fed. Each animals take on specialized roles to ensure the entire group is fed. Is there any meaning difference between th...
The term "troop" can mean a group of soldiers, or it can mean an individual soldier (perhaps in this usage it was originally short for "trooper"). In fact, in modern usage, the plural "troops" alm...
What's the grammatical class of "we" when referring to a group in its entirety versus when referring to each individual member of the group. For example, if I said to my girlfriend: We w...
Imagine you were learning English as a foreign language; I'm sure you'd be told that (unless there is gender ambiguity) a female individual requires the possessive adjective "her". The only reason I can think of for using 'their' in a case like this would be to tease those who are annoyed by such solecisms.